--- title: Glossary description: "### [51 percent attack](https://bitcoindevelopers.org/encyclopedia/51-percent-attack/) ### [Majority attack](https://bitcoindevelopers.org/encyclopedia/majority-attack/) The ability of someone controlling a majority of network hash rate to revise transaction history and prevent new transactions from confirming. ### [Address](https://bitcoindevelopers.org/encyclopedia/address/) A 20-byte hash formatted using [Base58check](https://bitcoindevelopers.org/encyclopedia/base58check/) to produce either a…" url: "https://bitcoindevelopers.org/docs/reference/glossary/" updated: "2025-05-14" category: Reference --- # Glossary ### [51 percent attack](https://bitcoindevelopers.org/encyclopedia/51-percent-attack/) ### [Majority attack](https://bitcoindevelopers.org/encyclopedia/majority-attack/) The ability of someone controlling a majority of network hash rate to revise transaction history and prevent new transactions from confirming. ### [Address](https://bitcoindevelopers.org/encyclopedia/address/) A 20-byte hash formatted using [Base58check](https://bitcoindevelopers.org/encyclopedia/base58check/) to produce either a P2PKH or P2SH Bitcoin [Address](https://bitcoindevelopers.org/encyclopedia/address/). Currently the most common way users exchange payment information. **Not to be confused with:** IP [Address](https://bitcoindevelopers.org/encyclopedia/address/) ### [Base58check](https://bitcoindevelopers.org/encyclopedia/base58check/) The method used in Bitcoin for converting 160-bit hashes into P2PKH and P2SH addresses. Also used in other parts of Bitcoin, such as encoding private keys for backup in WIP format. Not the same as other base58 implementations. **Not to be confused with:** P2PKH [Address](https://bitcoindevelopers.org/encyclopedia/address/), P2SH [Address](https://bitcoindevelopers.org/encyclopedia/address/), IP [Address](https://bitcoindevelopers.org/encyclopedia/address/) ### [Block](https://bitcoindevelopers.org/encyclopedia/block/) One or more transactions prefaced by a [Block](https://bitcoindevelopers.org/encyclopedia/block/) [Header](https://bitcoindevelopers.org/encyclopedia/header/) and protected by [Proof of work](https://bitcoindevelopers.org/encyclopedia/proof-of-work/). Blocks are the data stored on the [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain. ### [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain ### Best [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain A chain of blocks with each [Block](https://bitcoindevelopers.org/encyclopedia/block/) referencing the [Block](https://bitcoindevelopers.org/encyclopedia/block/) that preceded it. The most-difficult-to-recreate chain is the best [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain. **Not to be confused with:** [Header chain](https://bitcoindevelopers.org/encyclopedia/header-chain/) ### [Block](https://bitcoindevelopers.org/encyclopedia/block/) [Header](https://bitcoindevelopers.org/encyclopedia/header/) ### [Header](https://bitcoindevelopers.org/encyclopedia/header/) An 80-byte [Header](https://bitcoindevelopers.org/encyclopedia/header/) belonging to a single [Block](https://bitcoindevelopers.org/encyclopedia/block/) which is hashed repeatedly to create [Proof of work](https://bitcoindevelopers.org/encyclopedia/proof-of-work/). ### [Height](https://bitcoindevelopers.org/encyclopedia/height/) ### [Block height](https://bitcoindevelopers.org/encyclopedia/block-height/) The number of blocks preceding a particular [Block](https://bitcoindevelopers.org/encyclopedia/block/) on a [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain. For example, the genesis [Block](https://bitcoindevelopers.org/encyclopedia/block/) has a [Height](https://bitcoindevelopers.org/encyclopedia/height/) of zero because zero [Block](https://bitcoindevelopers.org/encyclopedia/block/) preceded it. ### [Block reward](https://bitcoindevelopers.org/encyclopedia/block-reward/) The amount that miners may claim as a reward for creating a [Block](https://bitcoindevelopers.org/encyclopedia/block/). Equal to the sum of the [Block](https://bitcoindevelopers.org/encyclopedia/block/) subsidy (newly available [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/)) plus the transactions fees paid by transactions included in the [Block](https://bitcoindevelopers.org/encyclopedia/block/). **Not to be confused with:** [Block](https://bitcoindevelopers.org/encyclopedia/block/) subsidy, Transaction fees ### [Maximum Block Size](https://bitcoindevelopers.org/encyclopedia/maximum-block-size/) The maximum size of a [Block](https://bitcoindevelopers.org/encyclopedia/block/) according to the [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/). The current [Block](https://bitcoindevelopers.org/encyclopedia/block/) size limit is 4 million weight units (1 million vbytes). **Not to be confused with:** [Block](https://bitcoindevelopers.org/encyclopedia/block/), Blockchain, Blockchain size ### [Blocks-first sync](https://bitcoindevelopers.org/encyclopedia/blocks-first-sync/) Synchronizing the [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain by downloading each [Block](https://bitcoindevelopers.org/encyclopedia/block/) from a [Peer](https://bitcoindevelopers.org/encyclopedia/peer/) and then validating it. **Not to be confused with:** [Headers-first sync](https://bitcoindevelopers.org/encyclopedia/headers-first-sync/) ### [Bloom filter](https://bitcoindevelopers.org/encyclopedia/bloom-filter/) A filter used primarily by [SPV](https://bitcoindevelopers.org/encyclopedia/spv/) clients to request only matching transactions and merkle blocks from full nodes. **Not to be confused with:** [Bloom filter](https://bitcoindevelopers.org/encyclopedia/bloom-filter/) (general computer science term, of which Bitcoin’s bloom filters are a specific implementation) ### [Chain code](https://bitcoindevelopers.org/encyclopedia/chain-code/) In HD wallets, 256 bits of entropy added to the public and private keys to help them generate secure child keys; the master [Chain code](https://bitcoindevelopers.org/encyclopedia/chain-code/) is usually derived from a seed along with the [Master private key](https://bitcoindevelopers.org/encyclopedia/master-private-key/) ### Change [Address](https://bitcoindevelopers.org/encyclopedia/address/) ### Change [Output](https://bitcoindevelopers.org/encyclopedia/output/) An [Output](https://bitcoindevelopers.org/encyclopedia/output/) in a transaction which returns [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/) to the spender, thus preventing too much of the [Input](https://bitcoindevelopers.org/encyclopedia/input/) value from going to transaction fees. **Not to be confused with:** [Address](https://bitcoindevelopers.org/encyclopedia/address/) reuse ### [Child key](https://bitcoindevelopers.org/encyclopedia/child-key/) ### Child [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/) ### Child [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/) In HD wallets, a key derived from a [Parent key](https://bitcoindevelopers.org/encyclopedia/parent-key/). The key can be either a [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/) or a [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/), and the key derivation may also require a [Chain code](https://bitcoindevelopers.org/encyclopedia/chain-code/). **Not to be confused with:** [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/) (derived from a [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/), not a [Parent key](https://bitcoindevelopers.org/encyclopedia/parent-key/)) ### [Coinbase](https://bitcoindevelopers.org/encyclopedia/coinbase/) A special field used as the sole [Input](https://bitcoindevelopers.org/encyclopedia/input/) for [Coinbase](https://bitcoindevelopers.org/encyclopedia/coinbase/) transactions. The [Coinbase](https://bitcoindevelopers.org/encyclopedia/coinbase/) allows claiming the [Block reward](https://bitcoindevelopers.org/encyclopedia/block-reward/) and provides up to 100 bytes for arbitrary data. **Not to be confused with:** [Coinbase](https://bitcoindevelopers.org/encyclopedia/coinbase/) transaction, [Coinbase](https://bitcoindevelopers.org/encyclopedia/coinbase/).com ### [Coinbase](https://bitcoindevelopers.org/encyclopedia/coinbase/) transaction ### [Generation transaction](https://bitcoindevelopers.org/encyclopedia/generation-transaction/) The first transaction in a [Block](https://bitcoindevelopers.org/encyclopedia/block/). Always created by a [Miner](https://bitcoindevelopers.org/encyclopedia/miner/), it includes a single [Coinbase](https://bitcoindevelopers.org/encyclopedia/coinbase/). **Not to be confused with:** [Coinbase](https://bitcoindevelopers.org/encyclopedia/coinbase/) (the unique part of a [Coinbase](https://bitcoindevelopers.org/encyclopedia/coinbase/) transaction) ### [CompactSize](https://bitcoindevelopers.org/encyclopedia/compactsize/) A type of variable-length integer commonly used in the Bitcoin P2P protocol and Bitcoin serialized data structures. **Not to be confused with:** VarInt (a data type Bitcoin Core uses for local data storage), Compact (the data type used for [nBits](https://bitcoindevelopers.org/encyclopedia/nbits/) in the [Block](https://bitcoindevelopers.org/encyclopedia/block/) [Header](https://bitcoindevelopers.org/encyclopedia/header/)) ### Compressed [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/) An ECDSA [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/) that is 33 bytes long rather than the 65 bytes of an uncompressed [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/). ### [Confirmation score](https://bitcoindevelopers.org/encyclopedia/confirmation-score/) ### [Confirmations](https://bitcoindevelopers.org/encyclopedia/confirmations/) ### [Confirmed transaction](https://bitcoindevelopers.org/encyclopedia/confirmed-transaction/) ### [Unconfirmed transaction](https://bitcoindevelopers.org/encyclopedia/unconfirmed-transaction/) A score indicating the number of blocks on the best [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain that would need to be modified to remove or modify a particular transaction. A [Confirmed transaction](https://bitcoindevelopers.org/encyclopedia/confirmed-transaction/) has a [Confirmation score](https://bitcoindevelopers.org/encyclopedia/confirmation-score/) of one or higher. ### [Consensus](https://bitcoindevelopers.org/encyclopedia/consensus/) When several nodes (usually most nodes on the network) all have the same blocks in their locally-validated best [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain. **Not to be confused with:** Social [Consensus](https://bitcoindevelopers.org/encyclopedia/consensus/) (often used in discussion among developers to indicate that most people agree with a particular plan), [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/) (the rules that allow nodes to maintain [Consensus](https://bitcoindevelopers.org/encyclopedia/consensus/)) ### [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/) The [Block](https://bitcoindevelopers.org/encyclopedia/block/) validation rules that full nodes follow to stay in [Consensus](https://bitcoindevelopers.org/encyclopedia/consensus/) with other nodes. **Not to be confused with:** [Consensus](https://bitcoindevelopers.org/encyclopedia/consensus/) (what happens when nodes follow the same [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/)) ### [Child pays for parent](https://bitcoindevelopers.org/encyclopedia/child-pays-for-parent/) ### [CPFP](https://bitcoindevelopers.org/encyclopedia/cpfp/) ### [Ancestor mining](https://bitcoindevelopers.org/encyclopedia/ancestor-mining/) Selecting transactions for [Mining](https://bitcoindevelopers.org/encyclopedia/mining/) not just based on their fees but also based on the fees of their ancestors (parents) and descendants (children). **Not to be confused with:** [Replace by fee](https://bitcoindevelopers.org/encyclopedia/replace-by-fee/), [RBF](https://bitcoindevelopers.org/encyclopedia/rbf/) ### [Denomination](https://bitcoindevelopers.org/encyclopedia/denomination/) ### [Bitcoins](https://bitcoindevelopers.org/encyclopedia/bitcoins/) ### [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/) Denominations of Bitcoin value, usually measured in fractions of a bitcoin but sometimes measured in multiples of a satoshi. One bitcoin equals 100,000,000 [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/). **Not to be confused with:** Binary bits, a unit of data with two possible values ### [Difficulty](https://bitcoindevelopers.org/encyclopedia/difficulty/) ### Network [Difficulty](https://bitcoindevelopers.org/encyclopedia/difficulty/) How difficult it is to find a [Block](https://bitcoindevelopers.org/encyclopedia/block/) relative to the [Difficulty](https://bitcoindevelopers.org/encyclopedia/difficulty/) of finding the easiest possible [Block](https://bitcoindevelopers.org/encyclopedia/block/). The easiest possible [Block](https://bitcoindevelopers.org/encyclopedia/block/) has a proof-of-work [Difficulty](https://bitcoindevelopers.org/encyclopedia/difficulty/) of 1. **Not to be confused with:** [Target](https://bitcoindevelopers.org/encyclopedia/target/) threshold (the value from which [Difficulty](https://bitcoindevelopers.org/encyclopedia/difficulty/) is calculated) ### [DNS seed](https://bitcoindevelopers.org/encyclopedia/dns-seed/) A DNS server which returns IP addresses of full nodes on the Bitcoin network to assist in [Peer](https://bitcoindevelopers.org/encyclopedia/peer/) discovery. **Not to be confused with:** HD [Wallet](https://bitcoindevelopers.org/encyclopedia/wallet/) seeds ### [Double spend](https://bitcoindevelopers.org/encyclopedia/double-spend/) A transaction that uses the same [Input](https://bitcoindevelopers.org/encyclopedia/input/) as an already broadcast transaction. The attempt of duplication, deceit, or conversion, will be adjudicated when only one of the transactions is recorded in the blockchain. ### [Escrow contract](https://bitcoindevelopers.org/encyclopedia/escrow-contract/) A transaction in which a spender and receiver place funds in a 2-of-2 (or other m-of-n) [Multisig](https://bitcoindevelopers.org/encyclopedia/multisig/) [Output](https://bitcoindevelopers.org/encyclopedia/output/) so that neither can spend the funds until they’re both satisfied with some external outcome. ### [Extended key](https://bitcoindevelopers.org/encyclopedia/extended-key/) ### Public [Extended key](https://bitcoindevelopers.org/encyclopedia/extended-key/) ### Private [Extended key](https://bitcoindevelopers.org/encyclopedia/extended-key/) In the context of HD wallets, a [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/) or [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/) extended with the [Chain code](https://bitcoindevelopers.org/encyclopedia/chain-code/) to allow them to derive child keys. ### [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) When two or more blocks have the same [Block height](https://bitcoindevelopers.org/encyclopedia/block-height/), forking the [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain. Typically occurs when two or more miners find blocks at nearly the same time. Can also happen as part of an attack. **Not to be confused with:** Hard [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (a change in [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/) that breaks security for nodes that don’t upgrade), Soft [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (a change in [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/) that weakens security for nodes that don’t upgrade), Software [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (when one or more developers permanently develops a codebase separately from other developers), Git [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (when one or more developers temporarily develops a codebase separately from other developers) ### Genesis [Block](https://bitcoindevelopers.org/encyclopedia/block/) ### [Block](https://bitcoindevelopers.org/encyclopedia/block/) 0 The first [Block](https://bitcoindevelopers.org/encyclopedia/block/) in the Bitcoin [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain. **Not to be confused with:** [Generation transaction](https://bitcoindevelopers.org/encyclopedia/generation-transaction/) (the first transaction in a [Block](https://bitcoindevelopers.org/encyclopedia/block/)) ### Hard [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) A permanent divergence in the [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain, commonly occurs when non-upgraded nodes can’t validate blocks created by upgraded nodes that follow newer [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/). **Not to be confused with:** [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (a regular [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) where all nodes follow the same [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/), so the [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) is resolved once one chain has more [Proof of work](https://bitcoindevelopers.org/encyclopedia/proof-of-work/) than another), Soft [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (a temporary divergence in the [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain caused by non-upgraded nodes not following new [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/)), Software [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (when one or more developers permanently develops a codebase separately from other developers), Git [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (when one or more developers temporarily develops a codebase separately from other developers ### Hardened [Extended key](https://bitcoindevelopers.org/encyclopedia/extended-key/) A variation on HD [Wallet](https://bitcoindevelopers.org/encyclopedia/wallet/) extended keys where only the hardened extended [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/) can derive child keys. This prevents compromise of the [Chain code](https://bitcoindevelopers.org/encyclopedia/chain-code/) plus any [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/) from putting the whole [Wallet](https://bitcoindevelopers.org/encyclopedia/wallet/) at risk. ### [HD protocol](https://bitcoindevelopers.org/encyclopedia/hd-protocol/) ### HD [Wallet](https://bitcoindevelopers.org/encyclopedia/wallet/) The Hierarchical Deterministic (HD) key creation and transfer protocol (BIP32), which allows creating child keys from parent keys in a hierarchy. Wallets using the [HD protocol](https://bitcoindevelopers.org/encyclopedia/hd-protocol/) are called HD wallets. ### [HD wallet seed](https://bitcoindevelopers.org/encyclopedia/hd-wallet-seed/) ### [Root seed](https://bitcoindevelopers.org/encyclopedia/root-seed/) A potentially-short value used as a seed to generate the [Master private key](https://bitcoindevelopers.org/encyclopedia/master-private-key/) and master [Chain code](https://bitcoindevelopers.org/encyclopedia/chain-code/) for an HD [Wallet](https://bitcoindevelopers.org/encyclopedia/wallet/). **Not to be confused with:** Mnemonic code / mnemonic seed (a binary [Root seed](https://bitcoindevelopers.org/encyclopedia/root-seed/) formatted as words to make it easier for humans to transcribe and possibly remember) ### [Header chain](https://bitcoindevelopers.org/encyclopedia/header-chain/) ### Best [Header chain](https://bitcoindevelopers.org/encyclopedia/header-chain/) A chain of [Block](https://bitcoindevelopers.org/encyclopedia/block/) headers with each [Header](https://bitcoindevelopers.org/encyclopedia/header/) linking to the [Header](https://bitcoindevelopers.org/encyclopedia/header/) that preceded it; the most-difficult-to-recreate chain is the best [Header chain](https://bitcoindevelopers.org/encyclopedia/header-chain/) **Not to be confused with:** [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain ### [Headers-first sync](https://bitcoindevelopers.org/encyclopedia/headers-first-sync/) Synchronizing the [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain by downloading [Block](https://bitcoindevelopers.org/encyclopedia/block/) headers before downloading the full blocks. **Not to be confused with:** [Blocks-first sync](https://bitcoindevelopers.org/encyclopedia/blocks-first-sync/) (Downloading entire blocks immediately without first getting their headers) ### [High-priority transaction](https://bitcoindevelopers.org/encyclopedia/high-priority-transaction/) ### [Free transaction](https://bitcoindevelopers.org/encyclopedia/free-transaction/) Transactions that don’t have to pay a [Transaction fee](https://bitcoindevelopers.org/encyclopedia/transaction-fee/) because their inputs have been idle long enough to accumulated large amounts of priority. Note: miners choose whether to accept free transactions. ### Initial [Block](https://bitcoindevelopers.org/encyclopedia/block/) download ### [IBD](https://bitcoindevelopers.org/encyclopedia/ibd/) The process used by a new [Node](https://bitcoindevelopers.org/encyclopedia/node/) (or long-offline [Node](https://bitcoindevelopers.org/encyclopedia/node/)) to download a large number of blocks to catch up to the tip of the best [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain. **Not to be confused with:** [Blocks-first sync](https://bitcoindevelopers.org/encyclopedia/blocks-first-sync/) (syncing includes getting any amount of blocks; [IBD](https://bitcoindevelopers.org/encyclopedia/ibd/) is only used for large numbers of blocks) ### [Input](https://bitcoindevelopers.org/encyclopedia/input/) ### [TxIn](https://bitcoindevelopers.org/encyclopedia/txin/) An [Input](https://bitcoindevelopers.org/encyclopedia/input/) in a transaction which contains three fields: an [Outpoint](https://bitcoindevelopers.org/encyclopedia/outpoint/), a [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) script, and a [Sequence number](https://bitcoindevelopers.org/encyclopedia/sequence-number/). The [Outpoint](https://bitcoindevelopers.org/encyclopedia/outpoint/) references a previous [Output](https://bitcoindevelopers.org/encyclopedia/output/) and the [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) script allows spending it. ### [Internal byte order](https://bitcoindevelopers.org/encyclopedia/internal-byte-order/) The standard order in which hash digests are displayed as strings—the same format used in serialized blocks and transactions. **Not to be confused with:** [RPC byte order](https://bitcoindevelopers.org/encyclopedia/rpc-byte-order/) (where the byte order is reversed) ### [Inventory](https://bitcoindevelopers.org/encyclopedia/inventory/) A data type identifier and a hash; used to identify transactions and blocks available for download through the Bitcoin P2P network. **Not to be confused with:** Inv [Message](https://bitcoindevelopers.org/encyclopedia/message/) (one of the P2P messages that transmits inventories) ### [Locktime](https://bitcoindevelopers.org/encyclopedia/locktime/) ### [nLockTime](https://bitcoindevelopers.org/encyclopedia/nlocktime/) Part of a transaction which indicates the earliest time or earliest [Block](https://bitcoindevelopers.org/encyclopedia/block/) when that transaction may be added to the [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain. ### [Mainnet](https://bitcoindevelopers.org/encyclopedia/mainnet/) The original and main network for Bitcoin transactions, where [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/) have real economic value. **Not to be confused with:** [Testnet](https://bitcoindevelopers.org/encyclopedia/testnet/) (an open network very similar to [Mainnet](https://bitcoindevelopers.org/encyclopedia/mainnet/) where [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/) have no value), [Regtest](https://bitcoindevelopers.org/encyclopedia/regtest/) (a private testing [Node](https://bitcoindevelopers.org/encyclopedia/node/) similar to [Testnet](https://bitcoindevelopers.org/encyclopedia/testnet/)) ### [Transaction malleability](https://bitcoindevelopers.org/encyclopedia/transaction-malleability/) ### [Transaction mutability](https://bitcoindevelopers.org/encyclopedia/transaction-mutability/) The ability of someone to change (mutate) unconfirmed transactions without making them invalid, which changes the transaction’s [Txid](https://bitcoindevelopers.org/encyclopedia/txid/), making child transactions invalid. **Not to be confused with:** BIP62 (a proposal for an optional new transaction version that reduces the set of known mutations for common transactions) ### [Miner](https://bitcoindevelopers.org/encyclopedia/miner/)-activated soft [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) ### [MASF](https://bitcoindevelopers.org/encyclopedia/masf/) A Soft [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) activated by through [Miner](https://bitcoindevelopers.org/encyclopedia/miner/) signalling. **Not to be confused with:** User Activated Soft [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (a soft [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) activated by flag day or [Node](https://bitcoindevelopers.org/encyclopedia/node/) enforcement instead of [Miner](https://bitcoindevelopers.org/encyclopedia/miner/) signalling.), [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (a regular [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) where all nodes follow the same [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/), so the [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) is resolved once one chain has more [Proof of work](https://bitcoindevelopers.org/encyclopedia/proof-of-work/) than another), Hard [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (a permanent divergence in the [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain caused by non-upgraded nodes not following new [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/)), Soft [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (a temporary divergence in the [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain caused by non-upgraded nodes not following new [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/)), Software [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (when one or more developers permanently develops a codebase separately from other developers), Git [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (when one or more developers temporarily develops a codebase separately from other developers ### Master [Chain code](https://bitcoindevelopers.org/encyclopedia/chain-code/) ### [Master private key](https://bitcoindevelopers.org/encyclopedia/master-private-key/) In HD wallets, the master [Chain code](https://bitcoindevelopers.org/encyclopedia/chain-code/) and [Master private key](https://bitcoindevelopers.org/encyclopedia/master-private-key/) are the two pieces of data derived from the [Root seed](https://bitcoindevelopers.org/encyclopedia/root-seed/). ### [Merkle block](https://bitcoindevelopers.org/encyclopedia/merkle-block/) A partial [Merkle tree](https://bitcoindevelopers.org/encyclopedia/merkle-tree/) connecting transactions matching a [Bloom filter](https://bitcoindevelopers.org/encyclopedia/bloom-filter/) to the [Merkle root](https://bitcoindevelopers.org/encyclopedia/merkle-root/) of a [Block](https://bitcoindevelopers.org/encyclopedia/block/). **Not to be confused with:** [MerkleBlock](https://bitcoindevelopers.org/encyclopedia/merkleblock/) [Message](https://bitcoindevelopers.org/encyclopedia/message/) (a P2P protocol [Message](https://bitcoindevelopers.org/encyclopedia/message/) that transmits a [Merkle block](https://bitcoindevelopers.org/encyclopedia/merkle-block/)) ### [Merkle root](https://bitcoindevelopers.org/encyclopedia/merkle-root/) The root [Node](https://bitcoindevelopers.org/encyclopedia/node/) of a [Merkle tree](https://bitcoindevelopers.org/encyclopedia/merkle-tree/), a descendant of all the hashed pairs in the tree. [Block](https://bitcoindevelopers.org/encyclopedia/block/) headers must include a valid [Merkle root](https://bitcoindevelopers.org/encyclopedia/merkle-root/) descended from all transactions in that [Block](https://bitcoindevelopers.org/encyclopedia/block/). **Not to be confused with:** [Merkle tree](https://bitcoindevelopers.org/encyclopedia/merkle-tree/) (the tree of which the [Merkle root](https://bitcoindevelopers.org/encyclopedia/merkle-root/) is the root [Node](https://bitcoindevelopers.org/encyclopedia/node/)), [Merkle block](https://bitcoindevelopers.org/encyclopedia/merkle-block/) (a partial merkle branch connecting the root to one or more leaves \[transactions\]) ### [Merkle tree](https://bitcoindevelopers.org/encyclopedia/merkle-tree/) A tree constructed by hashing paired data (the leaves), then pairing and hashing the results until a single hash remains, the [Merkle root](https://bitcoindevelopers.org/encyclopedia/merkle-root/). In Bitcoin, the leaves are almost always transactions from a single [Block](https://bitcoindevelopers.org/encyclopedia/block/). **Not to be confused with:** Partial merkle branch (a branch connecting one or more leaves to the root), [Merkle block](https://bitcoindevelopers.org/encyclopedia/merkle-block/) (a partial merkle branch connecting one or more transactions from a single [Block](https://bitcoindevelopers.org/encyclopedia/block/) to the [Block](https://bitcoindevelopers.org/encyclopedia/block/) [Merkle root](https://bitcoindevelopers.org/encyclopedia/merkle-root/)) ### [Message](https://bitcoindevelopers.org/encyclopedia/message/) [Header](https://bitcoindevelopers.org/encyclopedia/header/) The four [Header](https://bitcoindevelopers.org/encyclopedia/header/) fields prefixed to all messages on the Bitcoin P2P network. ### [Minimum relay fee](https://bitcoindevelopers.org/encyclopedia/minimum-relay-fee/) ### [Relay fee](https://bitcoindevelopers.org/encyclopedia/relay-fee/) The minimum [Transaction fee](https://bitcoindevelopers.org/encyclopedia/transaction-fee/) a transaction must pay (if it isn’t a [High-priority transaction](https://bitcoindevelopers.org/encyclopedia/high-priority-transaction/)) for a full [Node](https://bitcoindevelopers.org/encyclopedia/node/) to relay that transaction to other nodes. There is no one [Minimum relay fee](https://bitcoindevelopers.org/encyclopedia/minimum-relay-fee/)—each [Node](https://bitcoindevelopers.org/encyclopedia/node/) chooses its own policy. **Not to be confused with:** [Transaction fee](https://bitcoindevelopers.org/encyclopedia/transaction-fee/) (the [Minimum relay fee](https://bitcoindevelopers.org/encyclopedia/minimum-relay-fee/) is a policy setting that filters out transactions with too-low transaction fees) ### [Mining](https://bitcoindevelopers.org/encyclopedia/mining/) ### [Miner](https://bitcoindevelopers.org/encyclopedia/miner/) [Mining](https://bitcoindevelopers.org/encyclopedia/mining/) is the act of creating valid Bitcoin blocks, which requires demonstrating [Proof of work](https://bitcoindevelopers.org/encyclopedia/proof-of-work/), and miners are devices that mine or people who own those devices. ### [Multisig](https://bitcoindevelopers.org/encyclopedia/multisig/) ### Bare [Multisig](https://bitcoindevelopers.org/encyclopedia/multisig/) A [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/) that provides *n* number of pubkeys and requires the corresponding [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) script provide *m* minimum number signatures corresponding to the provided pubkeys. **Not to be confused with:** [P2SH multisig](https://bitcoindevelopers.org/encyclopedia/p2sh-multisig/) (a [Multisig](https://bitcoindevelopers.org/encyclopedia/multisig/) script contained inside P2SH), Advanced scripts that require multiple signatures without using OP_CHECKMULTISIG or OP_CHECKMULTISIGVERIFY ### [nBits](https://bitcoindevelopers.org/encyclopedia/nbits/) ### [Target](https://bitcoindevelopers.org/encyclopedia/target/) The [Target](https://bitcoindevelopers.org/encyclopedia/target/) is the threshold below which a [Block](https://bitcoindevelopers.org/encyclopedia/block/) [Header](https://bitcoindevelopers.org/encyclopedia/header/) hash must be in order for the [Block](https://bitcoindevelopers.org/encyclopedia/block/) to be valid, and [nBits](https://bitcoindevelopers.org/encyclopedia/nbits/) is the encoded form of the [Target](https://bitcoindevelopers.org/encyclopedia/target/) threshold as it appears in the [Block](https://bitcoindevelopers.org/encyclopedia/block/) [Header](https://bitcoindevelopers.org/encyclopedia/header/). **Not to be confused with:** [Difficulty](https://bitcoindevelopers.org/encyclopedia/difficulty/) (a number measuring the [Difficulty](https://bitcoindevelopers.org/encyclopedia/difficulty/) of finding a [Header](https://bitcoindevelopers.org/encyclopedia/header/) hash relative to the [Difficulty](https://bitcoindevelopers.org/encyclopedia/difficulty/) of finding a [Header](https://bitcoindevelopers.org/encyclopedia/header/) hash with the easiest [Target](https://bitcoindevelopers.org/encyclopedia/target/)) ### [Node](https://bitcoindevelopers.org/encyclopedia/node/) ### Full [Node](https://bitcoindevelopers.org/encyclopedia/node/) ### Archival [Node](https://bitcoindevelopers.org/encyclopedia/node/) ### Pruned [Node](https://bitcoindevelopers.org/encyclopedia/node/) ### [Peer](https://bitcoindevelopers.org/encyclopedia/peer/) A computer that connects to the Bitcoin network. **Not to be confused with:** Lightweight [Node](https://bitcoindevelopers.org/encyclopedia/node/), [SPV](https://bitcoindevelopers.org/encyclopedia/spv/) [Node](https://bitcoindevelopers.org/encyclopedia/node/) ### [Null data transaction](https://bitcoindevelopers.org/encyclopedia/null-data-transaction/) ### [OP_RETURN transaction](https://bitcoindevelopers.org/encyclopedia/op_return-transaction/) ### [Data carrier transaction](https://bitcoindevelopers.org/encyclopedia/data-carrier-transaction/) A transaction type relayed and mined by default in Bitcoin Core 0.9.0 and later that adds arbitrary data to a provably unspendable [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/) that full nodes don’t have to store in their [UTXO](https://bitcoindevelopers.org/encyclopedia/utxo/) database. **Not to be confused with:** OP_RETURN (an [Opcode](https://bitcoindevelopers.org/encyclopedia/opcode/) used in one of the outputs in an [OP_RETURN transaction](https://bitcoindevelopers.org/encyclopedia/op_return-transaction/)) ### [Opcode](https://bitcoindevelopers.org/encyclopedia/opcode/) ### Data-pushing [Opcode](https://bitcoindevelopers.org/encyclopedia/opcode/) ### Non-data-pushing [Opcode](https://bitcoindevelopers.org/encyclopedia/opcode/) Operation codes from the Bitcoin Script language which push data or perform functions within a [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/) or [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) script. ### [Orphan block](https://bitcoindevelopers.org/encyclopedia/orphan-block/) Blocks whose parent [Block](https://bitcoindevelopers.org/encyclopedia/block/) has not been processed by the local [Node](https://bitcoindevelopers.org/encyclopedia/node/), so they can’t be fully validated yet. **Not to be confused with:** Stale [Block](https://bitcoindevelopers.org/encyclopedia/block/) ### [Outpoint](https://bitcoindevelopers.org/encyclopedia/outpoint/) The data structure used to refer to a particular transaction [Output](https://bitcoindevelopers.org/encyclopedia/output/), consisting of a 32-byte [Txid](https://bitcoindevelopers.org/encyclopedia/txid/) and a 4-byte [Output index](https://bitcoindevelopers.org/encyclopedia/output-index/) number (vout). **Not to be confused with:** [Output](https://bitcoindevelopers.org/encyclopedia/output/) (an entire [Output](https://bitcoindevelopers.org/encyclopedia/output/) from a transaction), [TxOut](https://bitcoindevelopers.org/encyclopedia/txout/) (same as [Output](https://bitcoindevelopers.org/encyclopedia/output/)) ### [Output](https://bitcoindevelopers.org/encyclopedia/output/) ### [TxOut](https://bitcoindevelopers.org/encyclopedia/txout/) An [Output](https://bitcoindevelopers.org/encyclopedia/output/) in a transaction which contains two fields: a value field for transferring zero or more [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/) and a [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/) for indicating what conditions must be fulfilled for those [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/) to be further spent. **Not to be confused with:** [Outpoint](https://bitcoindevelopers.org/encyclopedia/outpoint/) (a reference to a particular [Output](https://bitcoindevelopers.org/encyclopedia/output/)) ### P2PKH [Address](https://bitcoindevelopers.org/encyclopedia/address/) ### P2PKH [Output](https://bitcoindevelopers.org/encyclopedia/output/) A Bitcoin payment [Address](https://bitcoindevelopers.org/encyclopedia/address/) comprising a hashed [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/), allowing the spender to create a standard [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/) that Pays To PubKey Hash (P2PKH). **Not to be confused with:** P2PK [Output](https://bitcoindevelopers.org/encyclopedia/output/) (an [Output](https://bitcoindevelopers.org/encyclopedia/output/) paying a [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/) directly), P2SH [Address](https://bitcoindevelopers.org/encyclopedia/address/), P2SH [Output](https://bitcoindevelopers.org/encyclopedia/output/) (an [Address](https://bitcoindevelopers.org/encyclopedia/address/) comprising a hashed script, and its corresponding [Output](https://bitcoindevelopers.org/encyclopedia/output/)) ### P2SH [Address](https://bitcoindevelopers.org/encyclopedia/address/) ### P2SH [Output](https://bitcoindevelopers.org/encyclopedia/output/) A Bitcoin payment [Address](https://bitcoindevelopers.org/encyclopedia/address/) comprising a hashed script, allowing the spender to create a standard [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/) that Pays To Script Hash (P2SH). The script can be almost any valid [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/). **Not to be confused with:** P2PK [Output](https://bitcoindevelopers.org/encyclopedia/output/) (an [Output](https://bitcoindevelopers.org/encyclopedia/output/) paying a [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/) directly), P2PKH [Address](https://bitcoindevelopers.org/encyclopedia/address/), P2PKH [Output](https://bitcoindevelopers.org/encyclopedia/output/) (an [Address](https://bitcoindevelopers.org/encyclopedia/address/) comprising a hashed pubkey, and its corresponding [Output](https://bitcoindevelopers.org/encyclopedia/output/)), [P2SH multisig](https://bitcoindevelopers.org/encyclopedia/p2sh-multisig/) (a particular instance of P2SH where the script uses a [Multisig](https://bitcoindevelopers.org/encyclopedia/multisig/) [Opcode](https://bitcoindevelopers.org/encyclopedia/opcode/)) ### [P2SH multisig](https://bitcoindevelopers.org/encyclopedia/p2sh-multisig/) A P2SH [Output](https://bitcoindevelopers.org/encyclopedia/output/) where the [Redeem script](https://bitcoindevelopers.org/encyclopedia/redeem-script/) uses one of the [Multisig](https://bitcoindevelopers.org/encyclopedia/multisig/) opcodes. Up until Bitcoin Core 0.10.0, [P2SH multisig](https://bitcoindevelopers.org/encyclopedia/p2sh-multisig/) scripts were standard transactions, but most other P2SH scripts were not. **Not to be confused with:** [Multisig](https://bitcoindevelopers.org/encyclopedia/multisig/) pubkey scripts (also called “bare [Multisig](https://bitcoindevelopers.org/encyclopedia/multisig/)”, these [Multisig](https://bitcoindevelopers.org/encyclopedia/multisig/) scripts don’t use P2SH encapsulation), P2SH (general P2SH, of which [P2SH multisig](https://bitcoindevelopers.org/encyclopedia/p2sh-multisig/) is a specific instance that was special cased up until Bitcoin Core 0.10.0) ### [Parent key](https://bitcoindevelopers.org/encyclopedia/parent-key/) ### Parent [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/) ### [Parent private key](https://bitcoindevelopers.org/encyclopedia/parent-private-key/) In HD wallets, a key used to derive child keys. The key can be either a [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/) or a [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/), and the key derivation may also require a [Chain code](https://bitcoindevelopers.org/encyclopedia/chain-code/). **Not to be confused with:** [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/) (derived from a [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/), not a [Parent key](https://bitcoindevelopers.org/encyclopedia/parent-key/)) ### [Payment protocol](https://bitcoindevelopers.org/encyclopedia/payment-protocol/) ### [Payment request](https://bitcoindevelopers.org/encyclopedia/payment-request/) The deprecated protocol defined in BIP70 (and other BIPs) which lets spenders get signed payment details from receivers. **Not to be confused with:** IP-to-IP [Payment protocol](https://bitcoindevelopers.org/encyclopedia/payment-protocol/) (an insecure, discontinued protocol included in early versions of Bitcoin) ### [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/) The private portion of a keypair which can create signatures that other people can verify using the [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/). **Not to be confused with:** [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/) (data derived from the [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/)), [Parent key](https://bitcoindevelopers.org/encyclopedia/parent-key/) (a key used to create child keys, not necessarily a [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/)) ### [Proof of work](https://bitcoindevelopers.org/encyclopedia/proof-of-work/) ### [POW](https://bitcoindevelopers.org/encyclopedia/pow/) A hash below a [Target](https://bitcoindevelopers.org/encyclopedia/target/) value which can only be obtained, on average, by performing a certain amount of brute force work—therefore demonstrating [Proof of work](https://bitcoindevelopers.org/encyclopedia/proof-of-work/). ### [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/) ### [ScriptPubKey](https://bitcoindevelopers.org/encyclopedia/scriptpubkey/) A script included in outputs which sets the conditions that must be fulfilled for those [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/) to be spent. Data for fulfilling the conditions can be provided in a [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) script. Pubkey Scripts are called a [ScriptPubKey](https://bitcoindevelopers.org/encyclopedia/scriptpubkey/) in code. **Not to be confused with:** Pubkey (a [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/), which can be used as part of a [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/) but don’t provide a programmable authentication mechanism), [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) script (a script that provides data to the [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/)) ### [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/) The public portion of a keypair which can be used to verify signatures made with the private portion of the keypair. **Not to be confused with:** [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/) (data from which the [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/) is derived), [Parent key](https://bitcoindevelopers.org/encyclopedia/parent-key/) (a key used to create child keys, not necessarily a [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/)) ### [Replace by fee](https://bitcoindevelopers.org/encyclopedia/replace-by-fee/) ### [RBF](https://bitcoindevelopers.org/encyclopedia/rbf/) ### Opt-in [Replace by fee](https://bitcoindevelopers.org/encyclopedia/replace-by-fee/) Replacing one version of an [Unconfirmed transaction](https://bitcoindevelopers.org/encyclopedia/unconfirmed-transaction/) with a different version of the transaction that pays a higher [Transaction fee](https://bitcoindevelopers.org/encyclopedia/transaction-fee/). May use BIP125 signaling. **Not to be confused with:** [Child pays for parent](https://bitcoindevelopers.org/encyclopedia/child-pays-for-parent/), [CPFP](https://bitcoindevelopers.org/encyclopedia/cpfp/) ### [Redeem script](https://bitcoindevelopers.org/encyclopedia/redeem-script/) ### [RedeemScript](https://bitcoindevelopers.org/encyclopedia/redeemscript/) A script similar in function to a [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/). One copy of it is hashed to create a P2SH [Address](https://bitcoindevelopers.org/encyclopedia/address/) (used in an actual [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/)) and another copy is placed in the spending [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) script to enforce its conditions. **Not to be confused with:** [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) script (a script that provides data to the [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/), which includes the [Redeem script](https://bitcoindevelopers.org/encyclopedia/redeem-script/) in a P2SH [Input](https://bitcoindevelopers.org/encyclopedia/input/)) ### [Regtest](https://bitcoindevelopers.org/encyclopedia/regtest/) ### [Regression test mode](https://bitcoindevelopers.org/encyclopedia/regression-test-mode/) A local testing environment in which developers can almost instantly generate blocks on demand for testing events, and can create private [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/) with no real-world value. **Not to be confused with:** [Testnet](https://bitcoindevelopers.org/encyclopedia/testnet/) (a global testing environment which mostly mimics [Mainnet](https://bitcoindevelopers.org/encyclopedia/mainnet/)) ### [RPC byte order](https://bitcoindevelopers.org/encyclopedia/rpc-byte-order/) A hash digest displayed with the byte order reversed; used in Bitcoin Core RPCs, many [Block](https://bitcoindevelopers.org/encyclopedia/block/) explorers, and other software. **Not to be confused with:** [Internal byte order](https://bitcoindevelopers.org/encyclopedia/internal-byte-order/) (hash digests displayed in their typical order; used in serialized blocks and serialized transactions) ### [Sequence number](https://bitcoindevelopers.org/encyclopedia/sequence-number/) Part of all transactions. A number intended to allow unconfirmed time-locked transactions to be updated before being finalized; not currently used except to disable [Locktime](https://bitcoindevelopers.org/encyclopedia/locktime/) in a transaction **Not to be confused with:** [Output index](https://bitcoindevelopers.org/encyclopedia/output-index/) number / vout (this is the 0-indexed number of an [Output](https://bitcoindevelopers.org/encyclopedia/output/) within a transaction used by a later transaction to refer to that specific [Output](https://bitcoindevelopers.org/encyclopedia/output/)) ### [Serialized block](https://bitcoindevelopers.org/encyclopedia/serialized-block/) A complete [Block](https://bitcoindevelopers.org/encyclopedia/block/) in its binary format—the same format used to calculate total [Block](https://bitcoindevelopers.org/encyclopedia/block/) byte size; often represented using hexadecimal. ### [Serialized transaction](https://bitcoindevelopers.org/encyclopedia/serialized-transaction/) ### [Raw transaction](https://bitcoindevelopers.org/encyclopedia/raw-transaction/) Complete transactions in their binary format; often represented using hexadecimal. Sometimes called raw format because of the various Bitcoin Core commands with “raw” in their names. ### [SIGHASH_ALL](https://bitcoindevelopers.org/encyclopedia/sighash_all/) Default [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) hash type which signs the entire transaction except any [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) scripts, preventing modification of the signed parts. ### [SIGHASH_ANYONECANPAY](https://bitcoindevelopers.org/encyclopedia/sighash_anyonecanpay/) A [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) hash type which signs only the current [Input](https://bitcoindevelopers.org/encyclopedia/input/). **Not to be confused with:** [SIGHASH_SINGLE](https://bitcoindevelopers.org/encyclopedia/sighash_single/) (which signs this [Input](https://bitcoindevelopers.org/encyclopedia/input/), its corresponding [Output](https://bitcoindevelopers.org/encyclopedia/output/), and other inputs partially) ### [SIGHASH_NONE](https://bitcoindevelopers.org/encyclopedia/sighash_none/) [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) hash type which only signs the inputs, allowing anyone to change the outputs however they’d like. ### [SIGHASH_SINGLE](https://bitcoindevelopers.org/encyclopedia/sighash_single/) [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) hash type that signs the [Output](https://bitcoindevelopers.org/encyclopedia/output/) corresponding to this [Input](https://bitcoindevelopers.org/encyclopedia/input/) (the one with the same index value), this [Input](https://bitcoindevelopers.org/encyclopedia/input/), and any other inputs partially. Allows modification of other outputs and the [Sequence number](https://bitcoindevelopers.org/encyclopedia/sequence-number/) of other inputs. **Not to be confused with:** [SIGHASH_ANYONECANPAY](https://bitcoindevelopers.org/encyclopedia/sighash_anyonecanpay/) (a flag to [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) hash types that only signs this single [Input](https://bitcoindevelopers.org/encyclopedia/input/)) ### [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) A value related to a [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/) which could only have reasonably been created by someone who has the [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/) that created that [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/). Used in Bitcoin to authorize spending [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/) previously sent to a [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/). ### [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) hash ### [Sighash](https://bitcoindevelopers.org/encyclopedia/sighash/) A flag to Bitcoin signatures that indicates what parts of the transaction the [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) signs. (The default is [SIGHASH_ALL](https://bitcoindevelopers.org/encyclopedia/sighash_all/).) The unsigned parts of the transaction may be modified. **Not to be confused with:** Signed hash (a hash of the data to be signed), [Transaction malleability](https://bitcoindevelopers.org/encyclopedia/transaction-malleability/) / [Transaction mutability](https://bitcoindevelopers.org/encyclopedia/transaction-mutability/) (although non-default [Sighash](https://bitcoindevelopers.org/encyclopedia/sighash/) flags do allow optional malleability, malleability comprises any way a transaction may be mutated) ### [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) script ### [ScriptSig](https://bitcoindevelopers.org/encyclopedia/scriptsig/) Data generated by a spender which is almost always used as variables to satisfy a [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/). [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) Scripts are called [ScriptSig](https://bitcoindevelopers.org/encyclopedia/scriptsig/) in code. **Not to be confused with:** ECDSA [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) (a [Signature](https://bitcoindevelopers.org/encyclopedia/signature/), which can be used as part of a [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/) in addition to other data) ### [SPV](https://bitcoindevelopers.org/encyclopedia/spv/) ### [Simplified Payment Verification](https://bitcoindevelopers.org/encyclopedia/simplified-payment-verification/) ### [Lightweight client](https://bitcoindevelopers.org/encyclopedia/lightweight-client/) ### [Thin client](https://bitcoindevelopers.org/encyclopedia/thin-client/) A method for verifying if particular transactions are included in a [Block](https://bitcoindevelopers.org/encyclopedia/block/) without downloading the entire [Block](https://bitcoindevelopers.org/encyclopedia/block/). The method is used by some lightweight Bitcoin clients. ### Soft [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) A softfork is a change to the bitcoin protocol wherein only previously valid blocks/transactions are made invalid. Since old nodes will recognise the new blocks as valid, a softfork is backward-compatible. **Not to be confused with:** [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (a regular [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) where all nodes follow the same [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/), so the [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) is resolved once one chain has more [Proof of work](https://bitcoindevelopers.org/encyclopedia/proof-of-work/) than another), Hard [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (a permanent divergence in the [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain caused by non-upgraded nodes not following new [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/)), Software [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (when one or more developers permanently develops a codebase separately from other developers), Git [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (when one or more developers temporarily develops a codebase separately from other developers ### Stale [Block](https://bitcoindevelopers.org/encyclopedia/block/) Blocks which were successfully mined but which aren’t included on the current best [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain, likely because some other [Block](https://bitcoindevelopers.org/encyclopedia/block/) at the same [Height](https://bitcoindevelopers.org/encyclopedia/height/) had its chain extended first. **Not to be confused with:** [Orphan block](https://bitcoindevelopers.org/encyclopedia/orphan-block/) (a [Block](https://bitcoindevelopers.org/encyclopedia/block/) whose previous (parent) hash field points to an unknown [Block](https://bitcoindevelopers.org/encyclopedia/block/), meaning the orphan can’t be validated) ### [Standard Transaction](https://bitcoindevelopers.org/encyclopedia/standard-transaction/) A transaction that passes Bitcoin Core’s IsStandard() and IsStandardTx() tests. Only standard transactions are mined or broadcast by peers running the default Bitcoin Core software. ### [Start string](https://bitcoindevelopers.org/encyclopedia/start-string/) ### [Network magic](https://bitcoindevelopers.org/encyclopedia/network-magic/) Four defined bytes which start every [Message](https://bitcoindevelopers.org/encyclopedia/message/) in the Bitcoin P2P protocol to allow seeking to the next [Message](https://bitcoindevelopers.org/encyclopedia/message/). ### [Testnet](https://bitcoindevelopers.org/encyclopedia/testnet/) A global testing environment in which developers can obtain and spend [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/) that have no real-world value on a network that is very similar to the Bitcoin [Mainnet](https://bitcoindevelopers.org/encyclopedia/mainnet/). **Not to be confused with:** [Regtest](https://bitcoindevelopers.org/encyclopedia/regtest/) (a local testing environment where developers can control [Block](https://bitcoindevelopers.org/encyclopedia/block/) generation) ### [Token](https://bitcoindevelopers.org/encyclopedia/token/) A [Token](https://bitcoindevelopers.org/encyclopedia/token/) is a programmable digital asset with its own codebase that resides on an already existing [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain. Tokens are used to help facilitate the creation of decentralized applications. **Not to be confused with:** [Bitcoins](https://bitcoindevelopers.org/encyclopedia/bitcoins/), [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/), Security [Token](https://bitcoindevelopers.org/encyclopedia/token/), Denominations ### [Transaction fee](https://bitcoindevelopers.org/encyclopedia/transaction-fee/) ### [Miners fee](https://bitcoindevelopers.org/encyclopedia/miners-fee/) The amount remaining when the value of all outputs in a transaction are subtracted from all inputs in a transaction; the fee is paid to the [Miner](https://bitcoindevelopers.org/encyclopedia/miner/) who includes that transaction in a [Block](https://bitcoindevelopers.org/encyclopedia/block/). **Not to be confused with:** [Minimum relay fee](https://bitcoindevelopers.org/encyclopedia/minimum-relay-fee/) (the lowest fee a transaction must pay to be accepted into the memory pool and relayed by Bitcoin Core nodes) ### [Txid](https://bitcoindevelopers.org/encyclopedia/txid/) An identifier used to uniquely identify a particular transaction; specifically, the sha256d hash of the transaction. **Not to be confused with:** [Outpoint](https://bitcoindevelopers.org/encyclopedia/outpoint/) (the combination of a [Txid](https://bitcoindevelopers.org/encyclopedia/txid/) with a vout used to identify a specific [Output](https://bitcoindevelopers.org/encyclopedia/output/)) ### User-activated soft [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) ### [UASF](https://bitcoindevelopers.org/encyclopedia/uasf/) A Soft [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) activated by flag day or [Node](https://bitcoindevelopers.org/encyclopedia/node/) enforcement instead of [Miner](https://bitcoindevelopers.org/encyclopedia/miner/) signalling. **Not to be confused with:** [Miner](https://bitcoindevelopers.org/encyclopedia/miner/) Activated Soft [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (a soft [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) activated through [Miner](https://bitcoindevelopers.org/encyclopedia/miner/) signalling), [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (a regular [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) where all nodes follow the same [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/), so the [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) is resolved once one chain has more [Proof of work](https://bitcoindevelopers.org/encyclopedia/proof-of-work/) than another), Hard [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (a permanent divergence in the [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain caused by non-upgraded nodes not following new [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/)), Soft [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (a temporary divergence in the [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain caused by non-upgraded nodes not following new [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/)), Software [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (when one or more developers permanently develops a codebase separately from other developers), Git [Fork](https://bitcoindevelopers.org/encyclopedia/fork/) (when one or more developers temporarily develops a codebase separately from other developers ### [UTXO](https://bitcoindevelopers.org/encyclopedia/utxo/) An Unspent Transaction [Output](https://bitcoindevelopers.org/encyclopedia/output/) ([UTXO](https://bitcoindevelopers.org/encyclopedia/utxo/)) that can be spent as an [Input](https://bitcoindevelopers.org/encyclopedia/input/) in a new transaction. **Not to be confused with:** [Output](https://bitcoindevelopers.org/encyclopedia/output/) (any [Output](https://bitcoindevelopers.org/encyclopedia/output/), whether spent or not. Outputs are a superset of UTXOs) ### [Wallet](https://bitcoindevelopers.org/encyclopedia/wallet/) Software that stores private keys and monitors the [Block](https://bitcoindevelopers.org/encyclopedia/block/) chain (sometimes as a client of a server that does the processing) to allow users to spend and receive [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/). **Not to be confused with:** HD [Wallet](https://bitcoindevelopers.org/encyclopedia/wallet/) (a protocol that allows all of a [Wallet](https://bitcoindevelopers.org/encyclopedia/wallet/)’s keys to be created from a single seed) ### [WIF](https://bitcoindevelopers.org/encyclopedia/wif/) ### [Wallet](https://bitcoindevelopers.org/encyclopedia/wallet/) Import Format A data interchange format designed to allow exporting and importing a single [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/) with a flag indicating whether or not it uses a compressed [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/). **Not to be confused with:** Extended private keys (which allow importing a hierarchy of private keys) ### [Watch-only address](https://bitcoindevelopers.org/encyclopedia/watch-only-address/) An [Address](https://bitcoindevelopers.org/encyclopedia/address/) or [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/) stored in the [Wallet](https://bitcoindevelopers.org/encyclopedia/wallet/) without the corresponding [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/), allowing the [Wallet](https://bitcoindevelopers.org/encyclopedia/wallet/) to watch for outputs but not spend them. ### [Bitcoin URI](https://bitcoindevelopers.org/encyclopedia/bitcoin-uri/) A URI which allows receivers to encode payment details so spenders don’t have to manually enter addresses and other details. ### [Certificate chain](https://bitcoindevelopers.org/encyclopedia/certificate-chain/) A chain of certificates connecting a individual’s [Leaf certificate](https://bitcoindevelopers.org/encyclopedia/leaf-certificate/) to the certificate authority’s [Root certificate](https://bitcoindevelopers.org/encyclopedia/root-certificate/). ### [Coinbase](https://bitcoindevelopers.org/encyclopedia/coinbase/) [Block height](https://bitcoindevelopers.org/encyclopedia/block-height/) The current [Block](https://bitcoindevelopers.org/encyclopedia/block/)’s [Height](https://bitcoindevelopers.org/encyclopedia/height/) encoded into the first bytes of the [Coinbase](https://bitcoindevelopers.org/encyclopedia/coinbase/) field. ### [Fiat](https://bitcoindevelopers.org/encyclopedia/fiat/) National currencies such as the dollar or euro. ### [Intermediate certificate](https://bitcoindevelopers.org/encyclopedia/intermediate-certificate/) A [Intermediate certificate](https://bitcoindevelopers.org/encyclopedia/intermediate-certificate/) authority certificate which helps connect a leaf (receiver) certificate to a [Root certificate](https://bitcoindevelopers.org/encyclopedia/root-certificate/) authority. ### [Key index](https://bitcoindevelopers.org/encyclopedia/key-index/) An index number used in the HD [Wallet](https://bitcoindevelopers.org/encyclopedia/wallet/) formula to generate child keys from a [Parent key](https://bitcoindevelopers.org/encyclopedia/parent-key/). ### [Key pair](https://bitcoindevelopers.org/encyclopedia/key-pair/) A [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/) and its derived [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/). ### [Label](https://bitcoindevelopers.org/encyclopedia/label/) The [Label](https://bitcoindevelopers.org/encyclopedia/label/) parameter of a bitcoin: URI which provides the spender with the receiver’s name (unauthenticated). ### [Leaf certificate](https://bitcoindevelopers.org/encyclopedia/leaf-certificate/) The end-[Node](https://bitcoindevelopers.org/encyclopedia/node/) in a [Certificate chain](https://bitcoindevelopers.org/encyclopedia/certificate-chain/); in the [Payment protocol](https://bitcoindevelopers.org/encyclopedia/payment-protocol/), it is the certificate belonging to the receiver of [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/). ### [Merge](https://bitcoindevelopers.org/encyclopedia/merge/) Spending, in the same transaction, multiple outputs which can be traced back to different previous spenders, leaking information about how many [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/) you control. ### [Merge avoidance](https://bitcoindevelopers.org/encyclopedia/merge-avoidance/) A strategy for selecting which outputs to spend that avoids merging outputs with different histories that could leak private information. ### [Message](https://bitcoindevelopers.org/encyclopedia/message/) A parameter of bitcoin: URIs which allows the receiver to optionally specify a [Message](https://bitcoindevelopers.org/encyclopedia/message/) to the spender. ### [Micropayment channel](https://bitcoindevelopers.org/encyclopedia/micropayment-channel/) term-micropayment-channel (contracts-guide) ([original target](https://bitcoin.org/en/contracts-guide#term-micropayment-channel)) ### [OP CHECKMULTISIG](https://bitcoindevelopers.org/encyclopedia/op-checkmultisig/) [Opcode](https://bitcoindevelopers.org/encyclopedia/opcode/) which returns true if one or more provided signatures (m) sign the correct parts of a transaction and match one or more provided public keys (n). ### [Output index](https://bitcoindevelopers.org/encyclopedia/output-index/) The sequentially-numbered index of outputs in a single transaction starting from 0. ### [PKI](https://bitcoindevelopers.org/encyclopedia/pki/) [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/) Infrastructure; usually meant to indicate the X.509 certificate system used for HTTP Secure (https). ### [Point function](https://bitcoindevelopers.org/encyclopedia/point-function/) The ECDSA function used to create a [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/) from a [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/). ### [PP amount](https://bitcoindevelopers.org/encyclopedia/pp-amount/) Part of the [Output](https://bitcoindevelopers.org/encyclopedia/output/) part of the PaymentDetails part of a [Payment protocol](https://bitcoindevelopers.org/encyclopedia/payment-protocol/) where receivers can specify the amount of [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/) they want paid to a particular [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/). ### [PP expires](https://bitcoindevelopers.org/encyclopedia/pp-expires/) The expires field of a PaymentDetails where the receiver tells the spender when the PaymentDetails expires. ### [PP memo](https://bitcoindevelopers.org/encyclopedia/pp-memo/) The memo fields of PaymentDetails, Payment, and PaymentACK which allow spenders and receivers to send each other memos. ### [PP merchant data](https://bitcoindevelopers.org/encyclopedia/pp-merchant-data/) The merchant_data part of PaymentDetails and Payment which allows the receiver to send arbitrary data to the spender in PaymentDetails and receive it back in Payments. ### [PP pki data](https://bitcoindevelopers.org/encyclopedia/pp-pki-data/) The pki_data field of a PaymentRequest which provides details such as certificates necessary to validate the request. ### [PP pki type](https://bitcoindevelopers.org/encyclopedia/pp-pki-type/) The [PKI](https://bitcoindevelopers.org/encyclopedia/pki/) field of a PaymentRequest which tells spenders how to validate this request as being from a specific recipient. ### [PP script](https://bitcoindevelopers.org/encyclopedia/pp-script/) The script field of a PaymentDetails where the receiver tells the spender what pubkey scripts to pay. ### [Previous block header hash](https://bitcoindevelopers.org/encyclopedia/previous-block-header-hash/) A field in the [Block](https://bitcoindevelopers.org/encyclopedia/block/) [Header](https://bitcoindevelopers.org/encyclopedia/header/) which contains the SHA256(SHA256()) hash of the previous [Block](https://bitcoindevelopers.org/encyclopedia/block/)’s [Header](https://bitcoindevelopers.org/encyclopedia/header/). ### [R parameter](https://bitcoindevelopers.org/encyclopedia/r-parameter/) The [Payment request](https://bitcoindevelopers.org/encyclopedia/payment-request/) parameter in a bitcoin: URI. ### [Receipt](https://bitcoindevelopers.org/encyclopedia/receipt/) A cryptographically-verifiable [Receipt](https://bitcoindevelopers.org/encyclopedia/receipt/) created using parts of a [Payment request](https://bitcoindevelopers.org/encyclopedia/payment-request/) and a [Confirmed transaction](https://bitcoindevelopers.org/encyclopedia/confirmed-transaction/). ### [Root certificate](https://bitcoindevelopers.org/encyclopedia/root-certificate/) A certificate belonging to a certificate authority (CA). ### SSL [Signature](https://bitcoindevelopers.org/encyclopedia/signature/) Signatures created and recognized by major SSL implementations such as OpenSSL. ### Stanndard [Block](https://bitcoindevelopers.org/encyclopedia/block/) relay The regular [Block](https://bitcoindevelopers.org/encyclopedia/block/) relay method: announcing a [Block](https://bitcoindevelopers.org/encyclopedia/block/) with an inv [Message](https://bitcoindevelopers.org/encyclopedia/message/) and waiting for a response. ### [Transaction version number](https://bitcoindevelopers.org/encyclopedia/transaction-version-number/) A version number prefixed to transactions to allow upgrading. ### [Unique Address](https://bitcoindevelopers.org/encyclopedia/unique-address/) [Address](https://bitcoindevelopers.org/encyclopedia/address/) which are only used once to protect privacy and increase security. ### [Unsolicited block push](https://bitcoindevelopers.org/encyclopedia/unsolicited-block-push/) When a [Miner](https://bitcoindevelopers.org/encyclopedia/miner/) sends a [Block](https://bitcoindevelopers.org/encyclopedia/block/) [Message](https://bitcoindevelopers.org/encyclopedia/message/) without sending an inv [Message](https://bitcoindevelopers.org/encyclopedia/message/) first. ### [URI qr code](https://bitcoindevelopers.org/encyclopedia/uri-qr-code/) A QR code containing a bitcoin: URI. ### [V2 block](https://bitcoindevelopers.org/encyclopedia/v2-block/) The current version of Bitcoin blocks. ### [x509certificates](https://bitcoindevelopers.org/encyclopedia/x509certificates/) ### term-[x509certificates](https://bitcoindevelopers.org/encyclopedia/x509certificates/) (developer-examples) ([original target](https://bitcoin.org/en/developer-examples#term-x509certificates)) --- ### Glossary Terms [51 percent attack](https://bitcoindevelopers.org/encyclopedia/51-percent-attack/), [Address](https://bitcoindevelopers.org/encyclopedia/address/), [Ancestor mining](https://bitcoindevelopers.org/encyclopedia/ancestor-mining/), [Archival node](https://bitcoindevelopers.org/encyclopedia/archival-node/), [Bare multisig](https://bitcoindevelopers.org/encyclopedia/bare-multisig/), [Base58check](https://bitcoindevelopers.org/encyclopedia/base58check/), [Best block chain](https://bitcoindevelopers.org/encyclopedia/best-block-chain/), [Best header chain](https://bitcoindevelopers.org/encyclopedia/best-header-chain/), [Bitcoin URI](https://bitcoindevelopers.org/encyclopedia/bitcoin-uri/), [Bitcoins](https://bitcoindevelopers.org/encyclopedia/bitcoins/), [Block](https://bitcoindevelopers.org/encyclopedia/block/), [Block 0](https://bitcoindevelopers.org/encyclopedia/block-0/), [Block chain](https://bitcoindevelopers.org/encyclopedia/block-chain/), [Block header](https://bitcoindevelopers.org/encyclopedia/block-header/), [Block height](https://bitcoindevelopers.org/encyclopedia/block-height/), [Block reward](https://bitcoindevelopers.org/encyclopedia/block-reward/), [Blocks-first sync](https://bitcoindevelopers.org/encyclopedia/blocks-first-sync/), [Bloom filter](https://bitcoindevelopers.org/encyclopedia/bloom-filter/), [Certificate chain](https://bitcoindevelopers.org/encyclopedia/certificate-chain/), [Chain code](https://bitcoindevelopers.org/encyclopedia/chain-code/), [Change address](https://bitcoindevelopers.org/encyclopedia/change-address/), [Change output](https://bitcoindevelopers.org/encyclopedia/change-output/), [Child key](https://bitcoindevelopers.org/encyclopedia/child-key/), [Child pays for parent](https://bitcoindevelopers.org/encyclopedia/child-pays-for-parent/), [Child private key](https://bitcoindevelopers.org/encyclopedia/child-private-key/), [Child public key](https://bitcoindevelopers.org/encyclopedia/child-public-key/), [Coinbase](https://bitcoindevelopers.org/encyclopedia/coinbase/), [Coinbase block height](https://bitcoindevelopers.org/encyclopedia/coinbase-block-height/), [Coinbase transaction](https://bitcoindevelopers.org/encyclopedia/coinbase-transaction/), [CompactSize](https://bitcoindevelopers.org/encyclopedia/compactsize/), [Compressed public key](https://bitcoindevelopers.org/encyclopedia/compressed-public-key/), [Confirmation score](https://bitcoindevelopers.org/encyclopedia/confirmation-score/), [Confirmations](https://bitcoindevelopers.org/encyclopedia/confirmations/), [Confirmed transaction](https://bitcoindevelopers.org/encyclopedia/confirmed-transaction/), [Consensus](https://bitcoindevelopers.org/encyclopedia/consensus/), [Consensus rules](https://bitcoindevelopers.org/encyclopedia/consensus-rules/), [CPFP](https://bitcoindevelopers.org/encyclopedia/cpfp/), [Data carrier transaction](https://bitcoindevelopers.org/encyclopedia/data-carrier-transaction/), [Data-pushing opcode](https://bitcoindevelopers.org/encyclopedia/data-pushing-opcode/), [Denomination](https://bitcoindevelopers.org/encyclopedia/denomination/), [Difficulty](https://bitcoindevelopers.org/encyclopedia/difficulty/), [DNS seed](https://bitcoindevelopers.org/encyclopedia/dns-seed/), [Double spend](https://bitcoindevelopers.org/encyclopedia/double-spend/), [Escrow contract](https://bitcoindevelopers.org/encyclopedia/escrow-contract/), [Extended key](https://bitcoindevelopers.org/encyclopedia/extended-key/), [Fiat](https://bitcoindevelopers.org/encyclopedia/fiat/), [Fork](https://bitcoindevelopers.org/encyclopedia/fork/), [Free transaction](https://bitcoindevelopers.org/encyclopedia/free-transaction/), [Full node](https://bitcoindevelopers.org/encyclopedia/full-node/), [Generation transaction](https://bitcoindevelopers.org/encyclopedia/generation-transaction/), [Genesis block](https://bitcoindevelopers.org/encyclopedia/genesis-block/), [Hard fork](https://bitcoindevelopers.org/encyclopedia/hard-fork/), [Hardened extended key](https://bitcoindevelopers.org/encyclopedia/hardened-extended-key/), [HD protocol](https://bitcoindevelopers.org/encyclopedia/hd-protocol/), [HD wallet](https://bitcoindevelopers.org/encyclopedia/hd-wallet/), [HD wallet seed](https://bitcoindevelopers.org/encyclopedia/hd-wallet-seed/), [Header](https://bitcoindevelopers.org/encyclopedia/header/), [Header chain](https://bitcoindevelopers.org/encyclopedia/header-chain/), [Headers-first sync](https://bitcoindevelopers.org/encyclopedia/headers-first-sync/), [Height](https://bitcoindevelopers.org/encyclopedia/height/), [High-priority transaction](https://bitcoindevelopers.org/encyclopedia/high-priority-transaction/), [IBD](https://bitcoindevelopers.org/encyclopedia/ibd/), [Initial block download](https://bitcoindevelopers.org/encyclopedia/initial-block-download/), [Input](https://bitcoindevelopers.org/encyclopedia/input/), [Intermediate certificate](https://bitcoindevelopers.org/encyclopedia/intermediate-certificate/), [Internal byte order](https://bitcoindevelopers.org/encyclopedia/internal-byte-order/), [Inventory](https://bitcoindevelopers.org/encyclopedia/inventory/), [Key index](https://bitcoindevelopers.org/encyclopedia/key-index/), [Key pair](https://bitcoindevelopers.org/encyclopedia/key-pair/), [Label](https://bitcoindevelopers.org/encyclopedia/label/), [Leaf certificate](https://bitcoindevelopers.org/encyclopedia/leaf-certificate/), [Lightweight client](https://bitcoindevelopers.org/encyclopedia/lightweight-client/), [Locktime](https://bitcoindevelopers.org/encyclopedia/locktime/), [Mainnet](https://bitcoindevelopers.org/encyclopedia/mainnet/), [Majority attack](https://bitcoindevelopers.org/encyclopedia/majority-attack/), [MASF](https://bitcoindevelopers.org/encyclopedia/masf/), [Master chain code](https://bitcoindevelopers.org/encyclopedia/master-chain-code/), [Master private key](https://bitcoindevelopers.org/encyclopedia/master-private-key/), [Maximum Block Size](https://bitcoindevelopers.org/encyclopedia/maximum-block-size/), [Merge](https://bitcoindevelopers.org/encyclopedia/merge/), [Merge avoidance](https://bitcoindevelopers.org/encyclopedia/merge-avoidance/), [Merkle block](https://bitcoindevelopers.org/encyclopedia/merkle-block/), [Merkle root](https://bitcoindevelopers.org/encyclopedia/merkle-root/), [Merkle tree](https://bitcoindevelopers.org/encyclopedia/merkle-tree/), [MerkleBlock](https://bitcoindevelopers.org/encyclopedia/merkleblock/), [Message](https://bitcoindevelopers.org/encyclopedia/message/), [Message header](https://bitcoindevelopers.org/encyclopedia/message-header/), [Micropayment channel](https://bitcoindevelopers.org/encyclopedia/micropayment-channel/), [Miner](https://bitcoindevelopers.org/encyclopedia/miner/), [Miner-activated soft fork](https://bitcoindevelopers.org/encyclopedia/miner-activated-soft-fork/), [Miners fee](https://bitcoindevelopers.org/encyclopedia/miners-fee/), [Minimum relay fee](https://bitcoindevelopers.org/encyclopedia/minimum-relay-fee/), [Mining](https://bitcoindevelopers.org/encyclopedia/mining/), [Multisig](https://bitcoindevelopers.org/encyclopedia/multisig/), [nBits](https://bitcoindevelopers.org/encyclopedia/nbits/), [Network difficulty](https://bitcoindevelopers.org/encyclopedia/network-difficulty/), [Network magic](https://bitcoindevelopers.org/encyclopedia/network-magic/), [nLockTime](https://bitcoindevelopers.org/encyclopedia/nlocktime/), [Node](https://bitcoindevelopers.org/encyclopedia/node/), [Non-data-pushing opcode](https://bitcoindevelopers.org/encyclopedia/non-data-pushing-opcode/), [Null data transaction](https://bitcoindevelopers.org/encyclopedia/null-data-transaction/), [OP CHECKMULTISIG](https://bitcoindevelopers.org/encyclopedia/op-checkmultisig/), [OP_RETURN transaction](https://bitcoindevelopers.org/encyclopedia/op_return-transaction/), [Opcode](https://bitcoindevelopers.org/encyclopedia/opcode/), [Opt-in replace by fee](https://bitcoindevelopers.org/encyclopedia/opt-in-replace-by-fee/), [Orphan block](https://bitcoindevelopers.org/encyclopedia/orphan-block/), [Outpoint](https://bitcoindevelopers.org/encyclopedia/outpoint/), [Output](https://bitcoindevelopers.org/encyclopedia/output/), [Output index](https://bitcoindevelopers.org/encyclopedia/output-index/), [P2PKH address](https://bitcoindevelopers.org/encyclopedia/p2pkh-address/), [P2PKH output](https://bitcoindevelopers.org/encyclopedia/p2pkh-output/), [P2SH address](https://bitcoindevelopers.org/encyclopedia/p2sh-address/), [P2SH multisig](https://bitcoindevelopers.org/encyclopedia/p2sh-multisig/), [P2SH output](https://bitcoindevelopers.org/encyclopedia/p2sh-output/), [Parent key](https://bitcoindevelopers.org/encyclopedia/parent-key/), [Parent private key](https://bitcoindevelopers.org/encyclopedia/parent-private-key/), [Parent public key](https://bitcoindevelopers.org/encyclopedia/parent-public-key/), [Payment protocol](https://bitcoindevelopers.org/encyclopedia/payment-protocol/), [Payment request](https://bitcoindevelopers.org/encyclopedia/payment-request/), [Peer](https://bitcoindevelopers.org/encyclopedia/peer/), [PKI](https://bitcoindevelopers.org/encyclopedia/pki/), [Point function](https://bitcoindevelopers.org/encyclopedia/point-function/), [POW](https://bitcoindevelopers.org/encyclopedia/pow/), [PP amount](https://bitcoindevelopers.org/encyclopedia/pp-amount/), [PP expires](https://bitcoindevelopers.org/encyclopedia/pp-expires/), [PP memo](https://bitcoindevelopers.org/encyclopedia/pp-memo/), [PP merchant data](https://bitcoindevelopers.org/encyclopedia/pp-merchant-data/), [PP pki data](https://bitcoindevelopers.org/encyclopedia/pp-pki-data/), [PP pki type](https://bitcoindevelopers.org/encyclopedia/pp-pki-type/), [PP script](https://bitcoindevelopers.org/encyclopedia/pp-script/), [Previous block header hash](https://bitcoindevelopers.org/encyclopedia/previous-block-header-hash/), [Private extended key](https://bitcoindevelopers.org/encyclopedia/private-extended-key/), [Private key](https://bitcoindevelopers.org/encyclopedia/private-key/), [Proof of work](https://bitcoindevelopers.org/encyclopedia/proof-of-work/), [Pruned node](https://bitcoindevelopers.org/encyclopedia/pruned-node/), [Pubkey script](https://bitcoindevelopers.org/encyclopedia/pubkey-script/), [Public extended key](https://bitcoindevelopers.org/encyclopedia/public-extended-key/), [Public key](https://bitcoindevelopers.org/encyclopedia/public-key/), [R parameter](https://bitcoindevelopers.org/encyclopedia/r-parameter/), [Raw transaction](https://bitcoindevelopers.org/encyclopedia/raw-transaction/), [RBF](https://bitcoindevelopers.org/encyclopedia/rbf/), [Receipt](https://bitcoindevelopers.org/encyclopedia/receipt/), [Redeem script](https://bitcoindevelopers.org/encyclopedia/redeem-script/), [RedeemScript](https://bitcoindevelopers.org/encyclopedia/redeemscript/), [Regression test mode](https://bitcoindevelopers.org/encyclopedia/regression-test-mode/), [Regtest](https://bitcoindevelopers.org/encyclopedia/regtest/), [Relay fee](https://bitcoindevelopers.org/encyclopedia/relay-fee/), [Replace by fee](https://bitcoindevelopers.org/encyclopedia/replace-by-fee/), [Root certificate](https://bitcoindevelopers.org/encyclopedia/root-certificate/), [Root seed](https://bitcoindevelopers.org/encyclopedia/root-seed/), [RPC byte order](https://bitcoindevelopers.org/encyclopedia/rpc-byte-order/), [Satoshis](https://bitcoindevelopers.org/encyclopedia/satoshis/), [ScriptPubKey](https://bitcoindevelopers.org/encyclopedia/scriptpubkey/), [ScriptSig](https://bitcoindevelopers.org/encyclopedia/scriptsig/), [Sequence number](https://bitcoindevelopers.org/encyclopedia/sequence-number/), [Serialized block](https://bitcoindevelopers.org/encyclopedia/serialized-block/), [Serialized transaction](https://bitcoindevelopers.org/encyclopedia/serialized-transaction/), [Sighash](https://bitcoindevelopers.org/encyclopedia/sighash/), [SIGHASH_ALL](https://bitcoindevelopers.org/encyclopedia/sighash_all/), [SIGHASH_ANYONECANPAY](https://bitcoindevelopers.org/encyclopedia/sighash_anyonecanpay/), [SIGHASH_NONE](https://bitcoindevelopers.org/encyclopedia/sighash_none/), [SIGHASH_SINGLE](https://bitcoindevelopers.org/encyclopedia/sighash_single/), [Signature](https://bitcoindevelopers.org/encyclopedia/signature/), [Signature hash](https://bitcoindevelopers.org/encyclopedia/signature-hash/), [Signature script](https://bitcoindevelopers.org/encyclopedia/signature-script/), [Simplified Payment Verification](https://bitcoindevelopers.org/encyclopedia/simplified-payment-verification/), [Soft fork](https://bitcoindevelopers.org/encyclopedia/soft-fork/), [SPV](https://bitcoindevelopers.org/encyclopedia/spv/), [SSL signature](https://bitcoindevelopers.org/encyclopedia/ssl-signature/), [Stale block](https://bitcoindevelopers.org/encyclopedia/stale-block/), [Standard Transaction](https://bitcoindevelopers.org/encyclopedia/standard-transaction/), [Stanndard block relay](https://bitcoindevelopers.org/encyclopedia/stanndard-block-relay/), [Start string](https://bitcoindevelopers.org/encyclopedia/start-string/), [Target](https://bitcoindevelopers.org/encyclopedia/target/), [Testnet](https://bitcoindevelopers.org/encyclopedia/testnet/), [Thin client](https://bitcoindevelopers.org/encyclopedia/thin-client/), [Token](https://bitcoindevelopers.org/encyclopedia/token/), [Transaction fee](https://bitcoindevelopers.org/encyclopedia/transaction-fee/), [Transaction malleability](https://bitcoindevelopers.org/encyclopedia/transaction-malleability/), [Transaction mutability](https://bitcoindevelopers.org/encyclopedia/transaction-mutability/), [Transaction version number](https://bitcoindevelopers.org/encyclopedia/transaction-version-number/), [Txid](https://bitcoindevelopers.org/encyclopedia/txid/), [TxIn](https://bitcoindevelopers.org/encyclopedia/txin/), [TxOut](https://bitcoindevelopers.org/encyclopedia/txout/), [UASF](https://bitcoindevelopers.org/encyclopedia/uasf/), [Unconfirmed transaction](https://bitcoindevelopers.org/encyclopedia/unconfirmed-transaction/), [Unique Address](https://bitcoindevelopers.org/encyclopedia/unique-address/), [Unsolicited block push](https://bitcoindevelopers.org/encyclopedia/unsolicited-block-push/), [URI qr code](https://bitcoindevelopers.org/encyclopedia/uri-qr-code/), [User-activated soft fork](https://bitcoindevelopers.org/encyclopedia/user-activated-soft-fork/), [UTXO](https://bitcoindevelopers.org/encyclopedia/utxo/), [V2 block](https://bitcoindevelopers.org/encyclopedia/v2-block/), [Wallet](https://bitcoindevelopers.org/encyclopedia/wallet/), [Wallet Import Format](https://bitcoindevelopers.org/encyclopedia/wallet-import-format/), [Watch-only address](https://bitcoindevelopers.org/encyclopedia/watch-only-address/), [WIF](https://bitcoindevelopers.org/encyclopedia/wif/), [x509certificates](https://bitcoindevelopers.org/encyclopedia/x509certificates/)