Crypto Glossary
Explore the essential crypto concepts you encounter in the news, with clear explanations and practical examples.
69 terms · Updated: September 10, 2026What Is Double Spending?
Term of the day · TransactionsDouble spending is the attempt to spend the same digital money in two different transactions. Bitcoin solves it without a central authority by recording transactions on a shared ledger secured by mining and block confirmations.
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What Is AML (Anti-Money Laundering) in Crypto?AML, or anti-money laundering, is the set of rules designed to stop criminal proceeds from being disguised as legitimate income and to prevent terrorist financing. Crypto exchanges apply it through identity checks, transaction monitoring and suspicious activity reports.
What Is APR and How Does It Differ from APY?APR, or annual percentage rate, is the simple yearly rate of return or cost of borrowing, without compounding. Crypto platforms use it for staking rewards and for interest on DeFi loans.
What Is APY and How Is It Calculated?APY, or annual percentage yield, is the yearly rate of return including the effect of compounding, assuming earnings are regularly reinvested. Crypto platforms use it to display staking, lending and DeFi yields.
What Does ATH (All-Time High) Mean in Crypto?ATH, short for all-time high, is the highest price an asset has reached since it started trading. When headlines say bitcoin hit a new ATH, the price has climbed to a level it had never reached before.
What Is ATL (All-Time Low)?ATL (all-time low) is the lowest price a cryptocurrency has reached since it started trading. It is the opposite of ATH and helps show an asset's full historical price range.
What Is an Atomic Swap?An atomic swap is a direct exchange of cryptocurrencies on two different blockchains without an intermediary, on an all-or-nothing basis. It relies on hash time-locked contracts (HTLCs) so neither side has to trust the other.
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What Is a Bear Market?A bear market is a prolonged period in which prices fall broadly and investor confidence weakens. In crypto, long bear markets are often called "crypto winters", and "bearish" describes an expectation of falling prices.
What Is Bitcoin Dominance?Bitcoin dominance is Bitcoin's market capitalization as a percentage of the total crypto market cap. It shows Bitcoin's relative weight in the market and is widely used to gauge shifts between Bitcoin and altcoins.
What Is a Block?A block is a batch of transactions recorded on a blockchain, together with the data needed to verify them. Each block contains the hash of the previous one, which links blocks into a chain.
What Is Blockchain Interoperability?Blockchain interoperability is the ability of separate blockchains to exchange data, messages and assets with each other. It is delivered through bridges, cross-chain messaging protocols and native standards such as IBC.
What Is a Blockchain Node?A node is a computer that connects to a blockchain network and runs its software. Nodes keep a copy of the chain, check new transactions and blocks against the network’s rules and share them with other nodes.
What Is a Blockchain Oracle?A blockchain oracle is a system that brings off-chain data, such as asset prices, sports results or weather, onto a blockchain so smart contracts can use it. Most DeFi protocols depend on oracles for prices.
What Is a Bull Market?A bull market is a sustained period in which prices rise broadly and investor optimism dominates. “Bullish” describes the view that an asset’s price will go up; its opposite is a bear market.
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What Is Circulating Supply?Circulating supply is the number of coins or tokens considered freely tradable in the market right now. Market cap is calculated by multiplying price by this figure; locked and unissued tokens are usually excluded.
What Is a Consensus Mechanism?A consensus mechanism is the set of rules that lets thousands of independent computers on a blockchain agree on which transactions are valid and in what order they are recorded, without a central authority.
What Is Crypto Custody?Crypto custody refers to who holds and protects the private keys that control a set of digital assets. If an exchange holds them, the service is custodial; if you hold them yourself, it is self-custody.
What Is a Crypto Wallet Address?A crypto wallet address is a unique string of letters and numbers that identifies where to send funds on a blockchain. Like a bank account number, it can be shared freely and does not grant spending rights.
What Is a Crypto Whale?A crypto whale is an individual or institution holding enough of a cryptocurrency to move its market price. Traders closely watch whales' large purchases, sales and transfers for clues about market direction.
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What Is a DAO and How Does It Work?A DAO, or decentralized autonomous organization, is an internet-native group whose rules are encoded in smart contracts and whose decisions are made by member votes, usually by token holders. DAOs manage treasuries and protocol decisions.
What Is a dApp (Decentralized Application)?A dApp, or decentralized application, is an app that runs its core functions on blockchain smart contracts instead of a company’s servers. Users connect their own wallet to swap, lend or trade NFTs without opening an account.
What Is Double Spending?Double spending is the attempt to spend the same digital money in two different transactions. Bitcoin solves it without a central authority by recording transactions on a shared ledger secured by mining and block confirmations.
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What is ERC-20?ERC-20 is the technical standard for creating fungible tokens on Ethereum. Because thousands of tokens such as USDT, USDC, LINK and UNI follow it, wallets and exchanges can support them all in the same way.
What is ERC-721?ERC-721 is the Ethereum standard for non-fungible tokens (NFTs): tokens that are each unique and not interchangeable. Every ERC-721 token has its own ID and a single owner recorded on-chain.
What Is EVM?The Ethereum Virtual Machine (EVM) is the execution environment that runs smart contract code on Ethereum and keeps every node in agreement on the result. EVM-compatible chains can use the same wallets and apps.
What Is an Exploit in Crypto?An exploit is an attack that takes advantage of a vulnerability in software or protocol design to make a system behave in unintended ways. In crypto, it usually means draining funds through a smart contract bug.
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What Are Fan Tokens?Fan tokens are crypto assets issued by sports clubs to give supporters perks such as voting in club polls, exclusive content and reward campaigns. They do not grant ownership, dividends or any say in how the club is run.
What is Finality?Finality is the point at which a blockchain transaction can no longer be reversed or altered. On Bitcoin it is probabilistic and strengthens with each confirmation; on proof-of-stake chains like Ethereum, validator votes finalize blocks at set checkpoints.
What Is FOMO in Crypto?FOMO (fear of missing out) is the anxiety of missing an opportunity. In crypto, it describes the urge to buy hastily and without a plan when prices are rising fast and everyone else seems to be winning.
What is a Fork?A fork is a change to a blockchain's rules or a split of the chain into two branches. Forks range from brief, routine chain splits to permanent divisions that create new coins, such as Bitcoin Cash.
What Is FUD in Crypto?FUD stands for fear, uncertainty and doubt. In crypto, it refers to negative news, rumors and commentary about a coin or project that can push prices down and drive investors to sell.
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What Is a Hard Fork?A hard fork is a protocol change that introduces new rules incompatible with older validation standards.
What is a Hash?A hash is a fixed-length digital fingerprint produced by running data through a hash function. Blockchains use hashes to link blocks together, identify transactions and power proof-of-work mining.
What Does HODL Mean?HODL is crypto slang for holding an asset long term instead of selling during price swings. It began as a 2013 typo of “hold” on a Bitcoin forum and later became a backronym for “Hold On for Dear Life”.
What Is a Honeypot Token?A honeypot token is a scam crypto token that anyone can buy but hidden rules in its smart contract prevent ordinary holders from selling. Only addresses chosen by the developer can cash out.
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What is a Mainnet?A mainnet is a blockchain's live, public network, where assets have real value, transactions are permanent and fees are paid in real coins. It is distinct from a testnet, which is used for development and experiments.
What Is Maximum Supply?Maximum supply is the highest number of units a cryptocurrency can ever have under its protocol or smart contract rules. Bitcoin’s 21 million cap is the best-known example; some networks, such as Ethereum, have no fixed cap.
What is a Mempool?A mempool is the waiting area where nodes hold transactions that have been broadcast but not yet included in a block. When the network is busy the mempool grows, and fees largely decide which transactions confirm first.
What is Mining Difficulty?Mining difficulty measures how hard it is to find a valid block on a proof-of-work blockchain. Bitcoin recalculates it every 2,016 blocks to keep the average time between blocks close to ten minutes.
What Is a Multisig Wallet?Multisig (multi-signature) is a security setup that requires approval from more than one private key before funds can move. In a 2-of-3 multisig, any two of three keys must sign each transaction.
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What Is a Passphrase in a Crypto Wallet?A passphrase is an optional extra password added to a wallet’s recovery phrase, sometimes called the “25th word”. Each passphrase creates a completely different wallet, so a stolen seed phrase alone is not enough to reach your funds.
What Is a Private Key?A private key is the secret cryptographic key that authorizes spending from a crypto wallet and signs its transactions. Anyone who knows a wallet's private key can move the funds it controls.
What is Proof of Work (PoW)?Proof of Work is a consensus mechanism in which miners earn the right to add new blocks by performing large amounts of computation. Bitcoin's security rests on the cost this imposes on anyone trying to rewrite history.
What is Proof of Stake (PoS)?Proof of Stake is a consensus mechanism in which validators lock up the network's coin as collateral to earn the right to propose and verify blocks. Validators who break the rules can lose part of their stake.
What Is a Public Key?A public key is a shareable cryptographic key derived from a private key and used to verify digital signatures. On most blockchains, wallet addresses are generated from the public key.
What Is a Pump and Dump?A pump and dump is a market manipulation scheme in which organizers inflate an asset’s price through coordinated buying and misleading promotion, then sell to the latecomers at the top. It is common in thinly traded tokens.
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What Is a Reentrancy Attack?Reentrancy is a smart contract vulnerability in which a contract can be called again before it finishes updating its own records. Attackers use it to withdraw the same funds repeatedly in a single transaction.
What is a Rollup?A rollup is a scaling solution that processes transactions off a main blockchain in batches, then posts the results and supporting data back to it. Ethereum layer-2 networks such as Arbitrum, Optimism, Base and zkSync are rollups.
What Is a Rug Pull?A rug pull is a crypto scam in which a project's developers take investors' money and abruptly abandon the project. It usually happens by draining the token's liquidity pool or dumping the team's token supply.
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What Is SegWit?SegWit (Segregated Witness) is a Bitcoin upgrade, activated in 2017, that moves signature data into a separate part of each transaction. It fixed transaction malleability, expanded block capacity and lowered fees.
What Is a Sequencer?A sequencer is the component of a Layer 2 network that collects user transactions, decides their order, executes them and posts them in batches to the base chain. It is what gives rollup users near-instant confirmations.
What Is a Smart Contract?A smart contract is a program stored on a blockchain that runs automatically when predefined conditions are met. It lets token transfers, swaps, lending and NFTs work without an intermediary.
What Is a Soft Fork?A soft fork is a blockchain change that narrows the rules for valid transactions or blocks while maintaining specific backward compatibility characteristics.
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What Is a Testnet?A testnet is a version of a blockchain that runs on tokens with no real value. Developers use it to test smart contracts and network upgrades before mainnet, and users can try new apps without risking money.
What Is Token Burning?Token burning permanently removes tokens from supply by sending them to an address nobody can spend from or by destroying them through a contract function. Ethereum’s fee burn is the best-known example.
What Is a Token Unlock?A token unlock is the moment previously locked tokens become transferable and sellable, usually under a vesting schedule. Large unlocks can quickly increase circulating supply, so markets track them closely.
What Is Token Vesting?Vesting is the process by which tokens allocated to a team, investors or advisers become available gradually on a preset schedule rather than all at once. A cliff is the initial period before anything unlocks.
What Is a Transaction Confirmation?A transaction confirmation shows that a crypto transfer has been included in a block, and how many blocks have been added on top since. The more confirmations, the harder the transaction is to reverse.
What Is TVL (Total Value Locked)?TVL, or total value locked, is the dollar value of all assets deposited in a DeFi protocol or across a blockchain’s protocols. It is used to compare size and usage, but it measures neither revenue nor security.
What is TXID?A TXID, or transaction ID, is a unique identifier for a blockchain transaction, created by hashing the transaction data. You use it to look up a transfer on a block explorer and to prove a payment was sent.
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What Is a Validator?A validator is a participant in a proof-of-stake blockchain that proposes new blocks and attests to others’ blocks. Validators stake the network’s native asset, earn rewards for honest work and can be slashed for breaking rules.
What Is Volatility in Crypto?Volatility measures how much and how quickly an asset's price swings over a given period. Cryptocurrencies are typically far more volatile than stocks or gold, which means bigger potential gains and losses.
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About the glossary
Learn the terms you encounter in the crypto world with simple definitions and brief examples. Concepts are listed alphabetically; you can type the term’s name or common abbreviation into the search field.
If you want to learn a process from start to finish, head over to the guides in the Learn Crypto section. For example, the “private key” entry explains the concept itself, while wallet security guides detail how to protect your keys and backups.