General & Fundamentals

1. The first decentralized cryptocurrency, introduced in a 2008 whitepaper by the pseudonymous Satoshi Nakamoto and launched on January 3, 2009. Bitcoin operates on a peer-to-peer network without a central authority, using a proof-of-work consensus mechanism to validate transactions and secure the network.

2. (lowercase: bitcoin) A unit of the Bitcoin currency. The total supply is capped at 21 million BTC, with new bitcoin issued as block rewards to miners approximately every 10 minutes. The issuance rate halves approximately every four years in an event known as the "halving."

See also: Satoshi Nakamoto · Proof of Work · Halving · Circulating Supply

1. A continuously growing list of records, called blocks, which are linked and secured using cryptographic hashes. Each block contains a cryptographic hash of the previous block, a timestamp, and transaction data — forming an immutable, append-only ledger distributed across a peer-to-peer network.

2. The foundational data structure underlying Bitcoin and most subsequent cryptocurrency networks. A blockchain achieves consensus among untrusted parties without a central authority by requiring network participants to validate and agree on the state of the ledger through a defined consensus mechanism.

See also: Distributed Ledger Technology · Merkle Tree · Consensus Mechanism · Satoshi Nakamoto

1. A fault-tolerant algorithm or protocol by which all nodes in a distributed blockchain network reach agreement on the single true state of the ledger. Consensus mechanisms solve the Byzantine Generals Problem — achieving reliable agreement among untrusted, potentially adversarial participants without a central coordinator.

2. The set of rules governing how new blocks are proposed, validated, and appended to the blockchain. The choice of consensus mechanism fundamentally determines a network's security model, energy consumption, throughput, and decentralization properties.

See also: Proof of Work · Proof of Stake · Byzantine Fault Tolerance

1. A digital or virtual currency secured by cryptography, operating on a decentralized network — typically a blockchain — that functions without a central issuing authority such as a government or financial institution. Cryptocurrencies use cryptographic techniques to control the creation of new units and verify the transfer of assets.

2. Broadly, any digital asset that uses cryptographic proof rather than institutional trust as its security model. The term encompasses coins (native assets of a Layer 1 blockchain) and tokens (assets issued on top of an existing blockchain platform).

See also: Bitcoin · Token · Howey Test · Market Capitalization

1. The distribution of authority, control, and decision-making across a network of participants rather than a single central entity. In blockchain systems, decentralization refers to the degree to which no single node, entity, or group of entities can unilaterally control, censor, or alter the network's state or rules.

2. A spectrum property, not a binary state. Networks are evaluated on multiple axes: architectural (number and distribution of nodes), political (number of individuals or organizations controlling nodes), and logical (whether the system behaves as a single monolithic object or a swarm).

See also: Blockchain Trilemma · DAO · Node

1. A digital system for recording, sharing, and synchronizing data across multiple locations, institutions, or geographies without a central administrator. DLT is the broader category of technology of which blockchain is the most prominent implementation — not all DLTs are blockchains, but all blockchains are DLTs.

See also: Blockchain · Directed Acyclic Graph (DAG) · Node

1. Hard Fork: A permanent divergence in the blockchain protocol that is not backward-compatible. Nodes running the old software cannot validate blocks produced under the new rules, resulting in a permanent chain split if a significant portion of the network does not upgrade.

2. Soft Fork: A backward-compatible protocol upgrade in which new rules are a strict subset of the old rules. Old nodes can still validate new blocks, allowing the network to upgrade without a mandatory split. Soft forks require only a majority of miners or validators to adopt the new rules.

See also: The DAO Hack · The Vault · Consensus Mechanism

1. A cryptographic hash function is a mathematical algorithm that maps data of arbitrary size to a fixed-size output (the "hash" or "digest"). Hash functions used in blockchain systems must satisfy four properties: determinism, pre-image resistance (computationally infeasible to reverse), collision resistance (infeasible to find two inputs with the same output), and avalanche effect (small input changes produce drastically different outputs).

See also: Proof of Work · Merkle Tree · SHA-256

1. A long-term investment strategy characterized by retaining cryptocurrency holdings through market volatility rather than trading. Derived from a December 18, 2013 post on the Bitcointalk forum by user "GameKyuubi," who wrote "I AM HODLING" — a typographical error for "holding" that became a defining piece of crypto cultural vocabulary.

2. (backronym) Hold On for Dear Life — a post-hoc rationalization of the original typo, now used to describe the philosophical conviction that long-term holding outperforms active trading for most retail participants, particularly given the difficulty of timing volatile crypto markets.

See also: Diamond Hands · Market Cycle · Bitcointalk Forum

1. The process by which new transactions are verified and added to a proof-of-work blockchain, and by which new cryptocurrency units are created and distributed. Miners compete to solve a computationally intensive cryptographic puzzle — finding a nonce that produces a block hash below the current difficulty target — with the winning miner earning the block reward plus all transaction fees included in the block.

See also: Proof of Work · Hash Function · Halving · Mining Pool

1. Any computer or device that participates in a blockchain network by maintaining a copy of the ledger and communicating with other participants. Nodes collectively form the peer-to-peer network that validates transactions, enforces protocol rules, and propagates new blocks.

2. Full Node: Downloads and independently validates every block and transaction against the protocol's consensus rules since the genesis block — the backbone of network security. Light Nodes (SPV): Download only block headers and rely on full nodes for transaction verification, sacrificing trustlessness for reduced resource requirements.

See also: Decentralization · Validator · Peer-to-Peer Network

1. A secret alphanumeric string — typically 256 bits in length — that serves as the cryptographic proof of ownership for a cryptocurrency address. The private key is used to generate digital signatures that authorize transactions. Possession of the private key constitutes ownership of the associated funds — there is no recourse mechanism if a private key is lost or stolen.

2. In elliptic curve cryptography (as used by Bitcoin and Ethereum), the private key is a randomly generated 256-bit integer from which the corresponding public key is derived via elliptic curve multiplication. The public key is then hashed to produce the wallet address. This derivation is one-way — the private key cannot be computed from the public key or address.