Bitcoin glossary: 44 terms defined in plain English.
At a glance: use this glossary to decode a term, then follow its linked guide for the network, wallet, market, price-data or risk context behind it. Every definition opens into a complete, sourced explanation with an example you can actually use.
44Bitcoin terms explainedReviewed 2026-08-04
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Five terms unlock most Bitcoin conversations.
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B
Bitcoin
An open monetary network and the scarce digital unit accounted for by that network.
Open full explanation →Block
A validated batch of transactions linked to the block before it.
Open full explanation →Block chain
Bitcoin's ordered, proof-of-work-protected record of blocks.
Open full explanation →Block height
The number of blocks before a block, starting with the genesis block at height zero.
Open full explanation →Block reward
The block subsidy plus transaction fees a miner may claim from a valid block.
Open full explanation →Block subsidy
New bitcoin a valid block is allowed to create under the issuance schedule.
Open full explanation →C
Cold storage
A custody setup that keeps spending keys away from internet-connected systems.
Open full explanation →Confirmation
Evidence that a transaction is in an accepted block, with depth added by later blocks.
Open full explanation →Consensus rules
The objective validation rules nodes use to accept or reject transactions and blocks.
Open full explanation →Custodial wallet
A service balance where another party controls the keys used to move the bitcoin.
Open full explanation →D
Difficulty
A measure derived from Bitcoin's proof-of-work target.
Open full explanation →Double-spend
An attempt to use the same transaction output in more than one conflicting transaction.
Open full explanation →F
Full node
Software that independently verifies Bitcoin blocks and transactions against its rules.
Open full explanation →H
Halving
The programmed 50% reduction in Bitcoin's block subsidy every 210,000 blocks.
Open full explanation →Hard fork
A rule change that can accept blocks older software would reject.
Open full explanation →Hardware wallet
A dedicated device that keeps private keys isolated while signing transactions.
Open full explanation →Hash
A fixed-size fingerprint produced by running data through a hash function.
Open full explanation →Hash rate
The rate at which mining hardware attempts proof-of-work hashes.
Open full explanation →L
Lightning invoice
A structured payment request used by Lightning wallets.
Open full explanation →Lightning Network
A payment-channel network for fast bitcoin payments that settle back to the base chain.
Open full explanation →M
Mempool
A node's local collection of valid, unconfirmed transactions.
Open full explanation →Miner
A person or system that builds candidate blocks and searches for valid proof of work.
Open full explanation →Mining pool
A service that combines miners' work to reduce the variance of payouts.
Open full explanation →Multisignature
A spending policy requiring more than one approved key.
Open full explanation →N
P
Private key
Secret numeric material used to authorize spending under a corresponding public key.
Open full explanation →Proof of work
Verifiable computational work that orders valid Bitcoin history.
Open full explanation →Public key
Cryptographic data used to verify a signature made by its private key.
Open full explanation →R
Replace-by-fee (RBF)
A relay policy that permits an unconfirmed transaction to be replaced by a fee-paying conflict.
Open full explanation →S
Satoshi (sat)
The smallest standard unit of bitcoin: 0.00000001 BTC.
Open full explanation →Seed phrase
A human-readable backup used by many wallets to derive a deterministic set of keys.
Open full explanation →Segregated Witness (SegWit)
A Bitcoin upgrade that separates signature data and introduced block weight accounting.
Open full explanation →Self-custody
Direct control of the keys required to spend your bitcoin.
Open full explanation →Soft fork
A backward-compatible tightening of consensus rules for non-upgraded nodes.
Open full explanation →T
Taproot
A Bitcoin upgrade combining Schnorr signatures with new script commitments and spending rules.
Open full explanation →Transaction
A signed data structure that spends existing outputs and creates new ones.
Open full explanation →Transaction fee
The input value not assigned to outputs, available to the block's miner.
Open full explanation →Transaction ID (TXID)
A hash-based identifier for a serialized Bitcoin transaction.
Open full explanation →U
UTXO
An unspent transaction output available to be used as a future input.
Open full explanation →W
Wallet
Software or hardware that manages keys and helps receive, construct, or sign transactions.
Open full explanation →Watch-only wallet
A wallet that can monitor funds and build transactions but cannot sign with private keys.
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Definitions built for understanding.
Each page separates the protocol fact from the practical meaning. Technical entries point to Bitcoin developer documentation or the relevant Bitcoin Improvement Proposal.