Bitcoin & crypto glossary

A situation where a single entity or group controls over 50% of the network’s mining power, potentially allowing them to manipulate the blockchain.

A public identifier used to direct a cryptocurrency payment. Address formats depend on the network. An address can be shared to receive funds; it is different from the private key that authorizes spending.

Any cryptocurrency other than Bitcoin.

A smart contract technology that enables the exchange of one cryptocurrency for another without the need for a centralized intermediary.

Bitcoin is a digital currency and peer-to-peer payment network launched in 2009. Its ticker is BTC. Transactions are recorded on a public blockchain: addresses are pseudonymous, so Bitcoin does not provide automatic anonymity.

A physical kiosk used to buy cryptocurrency with cash. Some machines also let users sell cryptocurrency for cash. Supported assets, fees, limits, and verification steps depend on the operator and location.

A cryptocurrency and payment network created by a split from Bitcoin in 2017. BCH and BTC operate on separate networks with different rules, so the two assets are not interchangeable.

A batch of transactions and associated data added to a blockchain. Blocks link to earlier blocks through cryptographic references, allowing nodes to check the ledger’s history.

A tool for looking up public blockchain information such as transactions, blocks, and addresses. Its results depend on the network and data it tracks; it does not control or recover your funds.

A block’s position in the chain, measured from the genesis block at height zero. It is an index, not a measure of the block’s file size.

For Bitcoin, the value a miner can claim for a valid block: the newly issued block subsidy plus the fees from transactions included in that block.

New cryptocurrency that a protocol permits a block producer to create. In Bitcoin, the subsidy follows a halving schedule and is separate from transaction fees.

A ledger organized into linked blocks, where each block refers cryptographically to the previous one. Consensus rules determine which additions the network’s participants accept.

A protocol that transfers messages or representations of assets between blockchain networks. Bridges use different verification and custody designs, so moving an asset across a bridge introduces assumptions beyond the original network.

A trading platform operated by a company that manages order matching and customer accounts. In a typical custodial exchange, the operator controls deposited assets until a withdrawal is processed.

A way of keeping a wallet’s private keys offline. Cold storage reduces exposure to online attacks, but the keys and recovery backup still need protection. The cryptocurrency itself remains recorded on its blockchain.

A transaction gains its first Bitcoin confirmation when it appears in a block on the accepted chain. Each later block adds another confirmation, making a reversal through chain reorganization progressively harder.

The process by which a blockchain network reaches agreement on a single data value or set of transactions.

A digital asset whose transfers and ownership are secured using cryptography and network rules. Bitcoin is one example; cryptocurrencies differ in their design, uses, issuance, and governance.

Mathematical techniques that protect information and verify its origin or integrity. Cryptography includes encryption, digital signatures, and hashing; it does not always involve making a message unreadable.

A wallet service where a provider holds or controls the keys on your behalf. You access funds through that provider’s account system and depend on it to process withdrawals.

An application that runs on a decentralized network, such as a blockchain, rather than on a centralized server.

Distribution of authority, information, and power across a network, rather than being held by a single central entity.

Financial systems that operate without central authorities, using blockchain technology.

A measure of how hard it is to find a valid proof-of-work block. Bitcoin periodically adjusts this target to keep average block production near its intended interval.

A cryptographic code that verifies the authenticity and integrity of a digital message or document.

A peer-to-peer cryptocurrency that began in 2013 with branding inspired by the Doge meme. DOGE is its native coin and is used for transfers, tipping, and payments.

A third-party service that holds funds or assets until the completion of a transaction or agreement.

The native cryptocurrency of Ethereum. Ether pays transaction fees and is used as stake in Ethereum’s proof-of-stake system. Ethereum is the network; ether is the asset.

Ethereum is a blockchain network that runs smart contracts and decentralized applications. Ether, abbreviated ETH, is its native currency and pays for network use. Ethereum uses proof of stake; the network and its currency are related but distinct.

Government-issued currency that is not backed by a physical commodity, such as USD, EUR, etc.

The feeling of urgency to invest in a rapidly appreciating asset.

A divergence in blockchain history or a change to a network’s rules. Competing blocks can create a temporary fork; protocol changes are commonly described as soft forks or hard forks.

Negative information or sentiment that may cause panic selling or discourage investment in a cryptocurrency.

Software that independently checks blocks and transactions against a blockchain’s rules. A Bitcoin full node can verify the network without mining, and it may prune old block files after validating them.

The first block in a blockchain, which serves as the foundation for all subsequent blocks.

A denomination of ether equal to one billion wei, or 0.000000001 ETH. Ethereum gas prices are commonly expressed in gwei.

A scheduled reduction of Bitcoin’s block subsidy by half every 210,000 blocks, roughly four years. It reduces newly issued bitcoin; transaction fees paid to miners are not halved by this event.

A rule change that can allow blocks older software rejects. Participants must adopt compatible rules to stay on the upgraded chain; disagreement can result in separate networks.

A physical device designed to keep private keys isolated and sign transactions without exposing those keys to the connected computer or phone. Its recovery backup is still needed if the device is lost.

A fixed-length output produced by a hash function from input data. In blockchains, cryptographic hashes help identify data and make changes detectable.

The number of hash calculations performed per second by mining equipment or an estimated network total. It measures computational activity in proof-of-work mining, not the number of transactions processed.

A slang term in the cryptocurrency community meaning to hold onto your investments rather than selling, even during market volatility.

A cryptocurrency wallet that is connected to the internet.

The process of verifying the identity of customers, often required by regulations for financial institutions.

A blockchain’s base network, where its own consensus rules establish the ledger. Bitcoin and Ethereum are examples. Additional protocols can build on a base layer to add payment or application capabilities.

A protocol built on a base blockchain to handle activity beyond the base layer while relying on it for settlement or security. Different designs inherit different protections and involve different assumptions.

A record-keeping system for tracking transactions and balances.

A payment network built on Bitcoin that routes payments through connected channels. Participants can make many offchain payments, while Bitcoin transactions establish and ultimately settle channel balances.

The ease with which an asset can be converted into cash without affecting its market price.

Crypto assets supplied to a smart contract so others can trade or use a protocol. Liquidity providers (LPs) may receive fees, but their holdings and returns can change as prices and pool balances move.

A peer-to-peer cryptocurrency and payment network derived from Bitcoin’s codebase. Its native coin is LTC, and its proof-of-work system uses the Scrypt hashing algorithm.

The primary network where actual transactions take place, as opposed to a testnet used for development and testing.

An asset’s quoted price multiplied by its circulating supply. Market capitalization is an estimate of market value, not the amount of cash invested or the amount that all holders could withdraw at once.

A node’s collection of transactions it has received and accepted but that are not yet confirmed in a block. Different nodes can have different mempools.

A data structure used in blockchain technology to efficiently and securely verify the integrity of large sets of data.

In proof-of-work networks, the process of assembling candidate blocks and repeatedly hashing them to find a valid proof of work. Other nodes independently check the resulting blocks and transactions.

A group of miners who combine their computational power to increase their chances of successfully mining a block and share the rewards.

A security feature that requires multiple keys to authorize a transaction.

A computer that participates in the blockchain network by validating and relaying transactions.

Services that provide external data to smart contracts, enabling them to interact with real-world information.

A decentralized network model where each participant (node) can act as both a client and a server.

A physical document containing a cryptocurrency address and private key, used for offline storage.

In BIP 39 wallets, an optional secret combined with the recovery words to derive a different wallet. It is separate from the device PIN; changing the passphrase changes the resulting wallet.

An arrangement that lets participants update balances without recording every payment on the base blockchain. Lightning uses linked payment channels to route payments between people who do not share a direct channel.

A secret key that is used to sign transactions and provide access to one’s cryptocurrency holdings.

A consensus approach in which validators commit cryptocurrency as stake to help secure a network. Protocol rules govern block proposals, voting, rewards, and penalties; staking does not guarantee a return.

A consensus mechanism that requires miners to solve complex mathematical problems to validate transactions and create new blocks.

A cryptographic value derived from a private key. It allows others to verify signatures made with that private key. A public key and a wallet address are related concepts, but are not identical.

A scheme where the price of a cryptocurrency is artificially inflated through false or misleading statements, followed by a rapid sell-off.

A sequence of words used by many wallets to recreate their keys. In BIP 39 wallets, the words and any optional passphrase derive a seed. Anyone with the necessary recovery information can control the wallet.

Replacing an unconfirmed Bitcoin transaction with another that spends overlapping inputs and pays a higher fee, subject to node policy. Wallet support and replacement rules affect whether the new transaction is accepted.

A scaling system that processes transactions outside Ethereum’s base execution layer and submits data and commitments or proofs to Ethereum. Optimistic and zero-knowledge rollups use different methods to establish correctness.

The smallest unit of Bitcoin, equal to 0.00000001 BTC, named after Bitcoin’s pseudonymous creator, Satoshi Nakamoto.

A Bitcoin upgrade that separates signature-related witness data from the base transaction structure. It changes transaction accounting and resolves forms of transaction malleability that previously complicated payment protocols.

An arrangement in which you control the keys or authorization needed to move your crypto, rather than relying on a custodian. You are responsible for keeping access and recovery information available and secure.

A scalability solution that divides a blockchain network into smaller, more manageable pieces, or “shards,” each capable of processing transactions in parallel.

The difference between a trade’s expected price and the price actually received when it executes. Slippage tolerance limits the permitted difference; it is separate from the price impact caused by the trade itself.

A program stored on a blockchain that executes according to the network’s rules when called. Smart contracts can manage assets or update data; external information generally reaches them through an oracle.

A protocol change that tightens existing validation rules. Upgraded nodes enforce the additional restrictions, while older nodes can still recognize compliant blocks as valid under the earlier rules.

Committing cryptocurrency to participate in a proof-of-stake network, directly or through a service. Rewards, withdrawal conditions, custody arrangements, and penalties depend on the protocol and the method used.

A Bitcoin upgrade that introduces a spending design using Schnorr signatures and script commitments. It can make certain complex spending conditions more efficient and reveal less information when the simple key-spending path is used.

An alternative blockchain used for testing and development, where developers can experiment without risking real assets.

A fee paid to the network for processing a transaction.

An identifier derived from a transaction’s data. You can use it to look up a transaction in a block explorer; it is not a private key or proof that a payment has confirmed.

An output from a Bitcoin transaction that has not yet been spent. A new transaction consumes earlier outputs and creates new ones, including any change returned to the sender.

A participant in a proof-of-stake network that performs duties such as proposing blocks or voting on their validity. Protocol-specific rules determine required stake, rewards, penalties, and removal.

Software or hardware that manages keys and helps you receive, sign, and send cryptocurrency transactions. Assets are recorded on the blockchain; a wallet manages access to them rather than storing coins inside the device.

An individual or entity that holds a large amount of cryptocurrency, capable of influencing market prices through their transactions.

A document that outlines the technical details and purpose of a cryptocurrency or blockchain project.