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A–Z Bitcoin glossary
32 Bitcoin terms explained in plain English. For the history behind them, see year by year and key events.
A
All-time high (ATH)
The highest price an asset has ever reached. Bitcoin sets new all-time highs in most bull markets. Learn more →
B
Bitcoin
The first and largest cryptocurrency: a digital money that runs on a network of computers with no central operator. The network is written Bitcoin (capital B) and the unit is written bitcoin or BTC.
Block
A bundle of transactions that miners add to the blockchain roughly every ten minutes. Each block refers to the one before it.
Block reward
The amount of new bitcoin a miner receives for adding a block, plus transaction fees. It is 3.125 BTC after the April 2024 halving.
Blockchain
The shared, public record of every Bitcoin block in order. Because each block depends on the previous one, changing history would mean redoing all the work after it.
Bull and bear markets
A bull market is a long stretch of rising prices; a bear market is a long stretch of falling prices, often defined as a drop of 20 percent or more from a peak. Learn more →
C
Cold storage
Keeping private keys on a device that is not connected to the internet, such as a hardware wallet, to protect them from online attacks.
Cypherpunk
A member of the movement, active since the 1990s, that advocated privacy and cryptography as tools for individual freedom. Bitcoin grew out of this community.
D
Difficulty adjustment
Every 2,016 blocks (about two weeks) the network resets how hard mining is so that blocks keep arriving about every ten minutes.
F
Fork
A change in the rules of a blockchain. A hard fork splits the network into incompatible chains, as happened when Bitcoin Cash split off in 2017.
G
Genesis block
Block 0, the first Bitcoin block, mined on January 3, 2009. It contains a newspaper headline as a timestamp. Learn more →
H
Halving
The event, roughly every four years or 210,000 blocks, when the reward for mining a block is cut in half. It slows the creation of new bitcoin until the 21 million limit is reached. Learn more →
Hash rate
The total computing power miners are using on the network, measured in hashes per second. A higher hash rate means a harder network to attack.
HODL
Holding Bitcoin through price swings instead of selling. The word began as a typo in a 2013 forum post and became a slogan.
L
Lightning Network
A second layer built on top of Bitcoin that allows fast, cheap payments by settling only occasionally on the main blockchain.
M
Market capitalization
The price of one coin multiplied by the number of coins in circulation. Used to compare the size of assets.
Mempool
The waiting room of transactions that have been broadcast but not yet included in a block.
Mining
The process of competing to add new blocks to the blockchain using computing power. Miners are paid in new bitcoin and transaction fees.
N
Node
A computer running Bitcoin software that checks every block and transaction against the rules and passes them on. Anyone can run one.
P
Private key
The secret number that proves you can spend a given bitcoin balance. Whoever holds it controls the coins.
Proof of work
The system that makes mining costly: miners must find a number that gives a block a valid hash. The cost of doing so is what protects the network from tampering.
S
Satoshi (sat)
The smallest unit of Bitcoin: one hundred-millionth of a bitcoin (0.00000001 BTC). Named after Satoshi Nakamoto.
Satoshi Nakamoto
The pseudonym of the person or group who published the Bitcoin white paper in 2008 and released the software in 2009. Their real identity is unknown. Learn more →
Seed phrase
A list of 12 or 24 words that can restore a wallet and its keys. It should be written down and kept offline and private.
SegWit
Segregated Witness, a 2017 upgrade that reorganised how transaction data is stored, fixed a bug called malleability and made room for more transactions per block.
Self-custody
Holding your own private keys rather than leaving coins with an exchange. Often summed up as “not your keys, not your coins.” Learn more →
Spot Bitcoin ETF
A fund traded on a stock exchange that holds actual bitcoin. US spot Bitcoin ETFs were approved in January 2024. Learn more →
T
Taproot
A 2021 upgrade that improved privacy and efficiency for complex transactions and made new kinds of smart contracts possible.
Transaction fee
A payment attached to a transaction so miners include it in a block. Fees rise when many people are trying to transact at once.
U
UTXO
Unspent transaction output: a chunk of bitcoin that has been received and not yet spent. Your balance is the sum of the UTXOs you control.
W
Wallet
Software or a device that holds your private keys and lets you send and receive bitcoin. The coins themselves live on the blockchain, not in the wallet.
Whale
A person or entity holding a very large amount of bitcoin, large enough that their trades can move the market.
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