A Bitcoin glossary is a reference that defines the protocol terms, wallet concepts, and network vocabulary you encounter when buying, holding, or using bitcoin, so you can read Bitcoin guides accurately and avoid costly mistakes.
This glossary covers wallet and self-custody terminology, on-chain transactions and fee mechanics, mining and block concepts, Lightning Network vocabulary, privacy terms, and common scam language. Each entry provides a plain-English definition, a concrete example, and the most common misconception to avoid. It does not provide trading advice, altcoin explanations, or legal or tax guidance specific to any jurisdiction.
How to use this glossary
Each term follows a consistent structure: a one-sentence definition, the mechanism behind it, a real-world example, and the most common beginner confusion. Terms are grouped by topic rather than alphabetically so you can build context progressively. If you already know the term you need, use the A-Z index near the bottom. For the informal community vocabulary not covered here (HODL, NGMI, stack sats, and similar), see our Bitcoin slang guide.
Notation used throughout:
"Bitcoin" (capital B) = the network and protocol
"bitcoin" (lowercase) or "BTC" = the asset you send and receive
"Lightning" = Bitcoin's layer-2 payment network
"on-chain" = recorded on the Bitcoin blockchain itself
What is bitcoin, and how are its units defined?
Bitcoin is both a decentralized payment protocol and the digital asset that moves on it. The distinction between these two layers prevents a persistent category of confusion when reading news coverage or technical documentation.
The Bitcoin network is a set of consensus rules enforced by thousands of full nodes worldwide. No company, government, or individual controls it. Bitcoin the asset, ticker symbol BTC, is the digital currency created and transferred according to those rules.
Bitcoin (BTC): Bitcoin refers to both the network protocol and the scarce digital asset that operates on it. When you read "the Bitcoin network processed 350,000 transactions today," the writer means the protocol. When you read "I sent 0.01 BTC," the writer means the asset. The two meanings share the same word, which causes persistent confusion for newcomers. For a broader treatment of what Bitcoin does and why it was created, see our guide on what Bitcoin is and the specific problems Bitcoin was designed to solve.
BTC and satoshis (sats): BTC is the primary denomination. One bitcoin contains exactly 100,000,000 satoshis (sats). Because bitcoin trades at prices that can exceed tens of thousands of dollars, most users, especially Lightning Network users, think in sats for everyday amounts. A 5,000-sat payment is clearer than "0.00005 BTC." The complete denomination breakdown is in BTC vs satoshis explained.
21 million supply cap: Bitcoin's protocol hard-codes a maximum supply of exactly 21 million BTC. No authority can issue more. Approximately 20.02 million BTC has been mined as of May 2026 (source: Bitinfocharts), leaving roughly 0.98 million BTC still to be issued through future block subsidies over the coming century.
Satoshi Nakamoto: The pseudonymous person or group who published the Bitcoin whitepaper in October 2008 and launched the network in January 2009. Nakamoto's identity remains unknown.
What is the blockchain and how does Bitcoin use it?
The blockchain is the data structure Bitcoin uses to record every transaction permanently without a central record-keeper.
Blockchain: A blockchain is a sequence of data blocks where each block contains a batch of validated transactions and cryptographically references the previous block through a hash pointer. Changing any historical block invalidates every subsequent hash, making undetected tampering practically impossible. Bitcoin's blockchain is one specific implementation with specific consensus rules, not a generic synonym for "crypto technology" broadly. For a technical breakdown, see how the Bitcoin blockchain works.
Distributed ledger: Bitcoin's blockchain is maintained simultaneously by thousands of full nodes worldwide. There is no master copy. Every full node holds an identical, independently verified copy. If one node goes offline or broadcasts a corrupted version, the rest reject it.
Peer-to-peer: Bitcoin transactions move directly between participants without a bank or payment processor routing them. No intermediary can freeze a payment or deny a recipient access.
Permissionless: Anyone can join the Bitcoin network, including sending transactions, receive funds, run a node, or mine, without registering, applying for approval, or identifying themselves to a central authority.
Trust-minimized: Bitcoin's design replaces institutional trust with cryptographic proof. You do not need to trust that a bank maintains accurate records; you can verify the blockchain yourself. "Trust-minimized" does not mean zero trust, you still trust that consensus rules are correctly implemented, but the trust required is far smaller and more auditable than in traditional finance.
Genesis block: The first Bitcoin block, mined by Satoshi Nakamoto on January 3, 2009. It contained a newspaper headline embedded as a message: "Chancellor on brink of second bailout for banks", a reference to the 2008 financial crisis that Bitcoin was, in part, a response to.
What are Bitcoin wallets, keys, and addresses?
This section covers the most security-critical concepts in Bitcoin. Errors here can cause permanent, irreversible loss of funds.
Wallet (software or hardware): A Bitcoin wallet is software or a dedicated device that manages your private key and generates receiving addresses. Wallets do not hold bitcoin the way a bank holds cash. Your bitcoin exists as unspent transaction output (UTXO) records on the blockchain. Your wallet holds the cryptographic keys that authorize you to spend those outputs. Losing your keys without a backup means losing access to your bitcoin permanently. See how to store bitcoin safely for practical custody guidance.
Custodial vs non-custodial (self-custody): A custodial wallet means a third party, typically an exchange, holds your private keys on your behalf. A non-custodial wallet means you hold the keys yourself. The phrase "not your keys, not your coins" captures the risk: if a custodian loses, freezes, or misappropriates your funds, you have no cryptographic recourse. The Mt. Gox exchange collapse in 2014 resulted in the loss of approximately 850,000 BTC held in customer accounts, a reminder that custodial risk is real. From a platform standpoint, every reputable exchange segments reserves between hot operational wallets and cold storage precisely because the custodial obligation is taken seriously. At BloFin, exchange-held balances are always custodial; we recommend transferring amounts not actively needed for trading to self-custody hardware storage.
Private key: A private key is a secret 256-bit number that proves ownership of specific bitcoin and authorizes the digital signature needed to spend it. There is no password reset, no customer support escalation, and no reversal mechanism. Anyone who obtains your private key controls the associated bitcoin permanently. Never share it, never type it into a website, and never store it in a photo or cloud service.
Public key: A public key is derived mathematically from the private key. It can be shared freely; it lets anyone verify that your digital signature is valid without revealing the private key. The derivation is one-way: a public key cannot be reverse-engineered into a private key. The full cryptographic relationship is in Bitcoin public key vs private key.
Bitcoin address: An address is a hashed encoding of your public key, typically 26-35 characters, that you share with others to receive bitcoin. Modern addresses use Bech32 format and start with "bc1". Best practice: generate a fresh address for every incoming transaction. Reusing the same address lets blockchain analysis tools link your transactions together, reducing privacy for you and every counterparty.
Seed phrase (mnemonic recovery phrase): A seed phrase (also called a recovery phrase or mnemonic) is a sequence of 12 or 24 human-readable words that encodes your master private key per the BIP-39 standard. Your seed phrase regenerates your entire wallet on any compatible software. It is equivalent in sensitivity to your private key itself. Storage rules: write it on paper or steel, store it offline in a secure physical location, never photograph it, never type it into any website or app, and never give it to any "support" contact under any circumstances. Full guidance is in what is a seed phrase.
Passphrase (25th word): An optional user-chosen word or phrase appended to your seed phrase, creating a separate encryption layer. Recovery requires both the seed phrase and the passphrase together. The security benefit is real: a stolen seed phrase without the passphrase reveals nothing spendable. The lockout risk is equally real: forgetting the passphrase makes the funds permanently inaccessible with no recovery path.
Hardware wallet: A hardware wallet is a dedicated physical device that generates your private key offline and signs transactions without ever exposing the key to an internet-connected computer. Even if your computer is infected with malware, the hardware wallet's isolated signing process prevents key theft. For a full comparison of hardware wallet types and security models, see what is a hardware wallet.
Cold storage vs hot wallet: Cold storage means your private key is kept entirely offline, including hardware wallets and air-gapped computers are the primary implementations. A hot wallet keeps keys on an internet-connected device (phone app, desktop software). Hot wallets offer spending convenience; cold storage protects long-term savings. Hot wallets suit day-to-day spending; cold storage protects long-term savings.
Multisig (multisignature): A multisig wallet configuration requires signatures from M of N designated private keys before a transaction can be authorized. A 2-of-3 multisig requires any two of three specified keys to sign, no single key has unilateral control. Multisig eliminates single points of failure and is used by organizations, family custody arrangements, and security-conscious individuals. The tradeoff: coordination becomes more complex, and losing track of key locations or quorum arrangements can lock funds permanently.
Digital signature: A digital signature is the cryptographic proof attached to a transaction showing that the sender controls the private key corresponding to the bitcoin being spent, without revealing that key. Bitcoin uses the Elliptic Curve Digital Signature Algorithm (ECDSA) and, since the 2021 Taproot upgrade, also supports Schnorr signatures. Every transaction on the blockchain contains at least one valid digital signature; nodes reject any transaction with an invalid one.
How do Bitcoin transactions work?
A Bitcoin transaction is a signed instruction to transfer specific bitcoin from one set of outputs to another. Understanding transactions prevents expensive mistakes like overpaying fees or misreading change addresses.
Transaction (tx): A Bitcoin transaction is a signed data structure referencing unspent outputs as inputs and creating new outputs assigned to recipient addresses. Every transaction is broadcast to the network, relayed by nodes, and eventually confirmed when a miner includes it in a block. The complete lifecycle, broadcast, mempool, confirmation, and settlement, is in how a Bitcoin transaction works.
UTXO (unspent transaction output): A UTXO is a discrete, indivisible chunk of bitcoin you have received but not yet spent. Your wallet balance is the sum of all your UTXOs. When you spend bitcoin, your wallet selects one or more UTXOs as inputs, spends them in full, and creates new outputs, one to the recipient and usually one back to you (the change output). A wallet holding many small UTXOs pays higher fees than one holding fewer large UTXOs, because each UTXO consumed as an input adds data weight to the transaction. The full UTXO mechanics are in the UTXO explainer.
Change output: Because UTXOs are spent in their entirety, any amount not sent to the recipient returns to you as a change output addressed to a fresh wallet address. If you have a 0.1 BTC UTXO and send 0.03 BTC, the transaction creates one output of ~0.03 BTC to the recipient and one output of roughly 0.07 BTC minus the fee to your change address. Beginners sometimes mistake a change output sent to an unfamiliar address for theft, it is not.
Confirmation: A confirmation occurs when the block containing your transaction is added to the blockchain. Each subsequent block on top counts as another confirmation. One confirmation means inclusion in a valid block but with theoretical reversal risk. For small purchases, 1–3 confirmations are typically accepted. For high-value transfers, 6 confirmations provide strong probabilistic finality, each confirmation adds exponentially more cost to any reversal attempt. The full confirmation security model is in Bitcoin confirmations explained.
Mempool: The mempool ("memory pool") is the queue of unconfirmed transactions that nodes hold until miners include them in a block. When you broadcast a transaction, it enters every connected node's mempool. Miners select transactions from the mempool in descending fee-rate order, because higher-fee transactions maximize their revenue per block. During high-demand periods, the 2021 bull run, the 2023 Ordinals inscription wave, mempools fill with tens of thousands of transactions, driving fee rates sharply higher. As of May 6, 2026, mempool.space shows approximately 50,000 unconfirmed transactions with minimum fees near 0.1 sat/vB, conditions currently mild (source: mempool.space).
Transaction fee and fee rate (sat/vB): The transaction fee is what you pay miners to include your transaction. It is measured as a fee rate in satoshis per virtual byte (sat/vB), where virtual bytes account for the SegWit witness data discount. A typical transaction consuming 1–2 UTXOs is 140–250 virtual bytes. At 5 sat/vB, that costs 700–1,250 sats. Setting a fee too low means waiting hours or days for confirmation; setting it too high wastes money. Check current mempool conditions before sending large amounts.
Double spend: A double spend is an attempt to spend the same bitcoin twice by broadcasting two conflicting transactions before either confirms. Bitcoin prevents this through the confirmation mechanism: once a transaction is buried under multiple blocks, replacing it would require re-doing all the proof-of-work for every subsequent block, infeasible at the network's current scale. Merchants accepting zero-confirmation payments carry higher double-spend exposure for large amounts.
RBF (Replace-By-Fee): Replace-By-Fee allows you to broadcast a higher-fee replacement for your own unconfirmed transaction. The original must have been flagged as RBF-enabled (opt-in RBF, per BIP-125) at broadcast time. If your transaction is stuck because you set too low a fee, RBF lets you re-send it with a higher fee rate without waiting. RBF does not create a new double-spend risk, it replaces your own pending transaction with a higher-priority version.
CPFP (Child Pays For Parent): If you received bitcoin in a stuck transaction (one your counterparty broadcast with too low a fee), you can spend that unconfirmed output immediately with a high enough fee that miners find the combined fee rate of both transactions attractive. This technique, child pays for parent, lets recipients accelerate someone else's stuck transaction even without RBF access.
Block: A block is a batch of validated transactions packaged by a miner and added to the Bitcoin blockchain. Each block references the previous block's hash, creating the chain. Blocks arrive on average every 10 minutes, though individual blocks vary significantly, a block might arrive in 1 minute or take 60+ minutes depending on mining variance. Each block has a size limit measured in weight units.
Block header: Each block contains a compact header with six fields: the protocol version, the previous block's hash, the Merkle root (a hash summarizing all transactions in the block), a Unix timestamp, the difficulty target, and the nonce miners vary to find a valid hash. The block header is what miners hash billions of times per second. Changing any single transaction in the block alters the Merkle root and invalidates the hash, this is how the blockchain's immutability property works in practice.
What is Bitcoin mining and how does consensus work?
Bitcoin mining is the process that creates new blocks, issues new bitcoin, and secures the transaction history against tampering. It is also the mechanism by which nodes agree on which history is valid.
Mining: Bitcoin mining is computational work performed by specialized hardware (ASICs (Application-Specific Integrated Circuits)) to find a valid block hash. Miners hash the block header with different nonce values until the result falls below the current difficulty target. The first miner to find a valid hash broadcasts the block; every node verifies it independently and adds it to their chain. In return, the winning miner earns the block subsidy plus all transaction fees in that block. Mining is not creating bitcoin arbitrarily, it is a competitive process that enforces the protocol and provides transaction ordering.
Proof of work (PoW): Proof of work is Bitcoin's consensus mechanism, the rule by which nodes agree on the valid transaction history. Each block must contain valid PoW: a hash meeting the difficulty requirement, proving the miner expended real computational energy. Rewriting history requires re-doing the PoW for every historical block while outpacing honest miners adding new ones, practically infeasible at current network scale. The detailed mechanism is in what is proof of work.
Hash and SHA-256: A hash function maps any input to a fixed-size output (a "digest"). Bitcoin uses SHA-256. Two properties matter: the same input always produces the same output, and any tiny change to the input produces a completely different output (the "avalanche effect"). You cannot reverse-engineer the input from the output. SHA-256 produces 256-bit digests, the number of possible hash values exceeds the number of atoms in the observable universe, which is why brute-force key cracking is infeasible.
Hash rate: Hash rate measures total computational work the Bitcoin network performs, expressed in hashes per second. As of May 2026, Bitcoin's network hash rate is approximately 997.55 exahashes per second (EH/s) (source: CoinWarz). This is more than double the ~400 EH/s figure from mid-2024, reflecting continued global hardware investment.
Difficulty: Difficulty is the numeric target controlling how hard it is to find a valid block hash. It adjusts every 2,016 blocks (roughly two weeks) to keep the average block time near 10 minutes regardless of total hash rate. If blocks arrive faster than 10 minutes on average, difficulty increases at the next adjustment. If blocks slow down, difficulty decreases. The current difficulty as of May 2026 is approximately 132.47 T (source: CoinWarz).
Block subsidy and coinbase transaction: The block subsidy is the fixed amount of newly created bitcoin awarded to each winning miner. Currently 3.125 BTC per block since the April 2024 halving. The coinbase transaction is the special first transaction in each block that creates this newly issued bitcoin and sends it to the miner's address. Disambiguation: "coinbase transaction" is a Bitcoin protocol term predating the Coinbase exchange by years; the two are entirely unrelated beyond sharing the name.
Halving: Every 210,000 blocks (roughly four years), Bitcoin's protocol halves the block subsidy. The history and schedule:
Block 0 (2009): 50 BTC per block
Block 210,000 (2012): 25 BTC
Block 420,000 (2016): 12.5 BTC
Block 630,000 (2020): 6.25 BTC
Block 840,000 (April 19, 2024): 3.125 BTC, mined by ViaBTC
Block 1,050,000 (~2028): 1.5625 BTC projected (likely March or April 2028)
Halvings reduce the rate of new bitcoin supply entering circulation. They do not guarantee price increases; past correlations between halvings and price rises do not ensure future results. Full context is in Bitcoin halving explained.
Consensus and the most-work chain: All nodes follow the chain with the most cumulative proof of work, sometimes simplified as the "longest chain" but technically the highest total-work chain. This rule resolves temporary forks when two miners find valid blocks simultaneously. Critically, consensus rules, like the 21 million supply cap, are enforced by every full node, not by miners. A miner who creates an invalid block gets it rejected regardless of hash rate.
51% attack: A 51% attack describes a scenario where an entity controlling more than half the network's hash rate could reorganize recent blocks, enabling double-spends or censorship. At current hash rates close to 1,000 EH/s, acquiring 51% would require hardware and electricity expenditure measured in tens of billions of dollars, economically irrational when honest mining generates predictable revenue. Deep reorganizations have never occurred on Bitcoin. See what is a 51% attack for the full threat model.
What are Bitcoin nodes and how do they enforce the rules?
Nodes are Bitcoin's enforcement layer. The distinction between nodes and miners explains why no single party, not even the largest mining pool, can unilaterally change Bitcoin's rules.
Full node: A full node is software (Bitcoin Core, the most widely deployed implementation) that downloads the complete Bitcoin blockchain, independently validates every block and transaction against consensus rules, and relays valid data to other nodes. Full nodes don't trust miners, they verify miners' work. If a miner submits an invalid block, every full node rejects it. Running your own node means you verify your own transaction history without trusting any third party. The roles and distinctions between nodes, miners, and wallets are in Bitcoin nodes vs miners vs wallets.
Bitcoin Core: Bitcoin Core is the reference implementation of the Bitcoin protocol, maintained by open-source contributors globally. Its consensus code, not any company or individual, defines what a valid Bitcoin transaction and block look like.
Lightweight (SPV) wallet: An SPV (Simplified Payment Verification) wallet downloads only block headers and relevant transaction proofs rather than the full blockchain. It trusts other nodes for validation rather than verifying everything independently. SPV wallets suit mobile use; a full node provides stronger guarantees for large holdings.
Fork (soft fork vs hard fork): A protocol change is called a fork because it splits the path of which rules nodes follow. A soft fork is backward-compatible, old nodes still accept blocks produced under new rules (though they don't understand new features). SegWit in 2017 was a soft fork that increased effective block capacity while remaining compatible with older node software. A hard fork requires all nodes to upgrade; any node that doesn't will follow a diverging chain with different rules. Bitcoin Cash in 2017 was a hard fork creating a separate network with larger block sizes. Comprehensive fork mechanics and historical examples are in Bitcoin forks explained.
Mempool policy vs consensus rules: Consensus rules are mandatory: no node may accept a block that violates them (such as creating more than the allowed block subsidy). Mempool policy is optional: individual nodes configure their own preferences for which unconfirmed transactions to relay, minimum fee thresholds, maximum transaction sizes, and similar settings. A transaction violating one node's policy may still propagate via others; a transaction violating consensus rules is rejected everywhere.
What do privacy and security terms mean in Bitcoin?
Bitcoin is pseudonymous, not anonymous. Transaction records are public and permanent. These terms matter because on-chain data, once recorded, cannot be deleted or changed.
Privacy vs anonymity: Privacy means controlling what information you reveal and to whom. Anonymity means acting with no attached identity at all. Bitcoin provides pseudonymity by default, transactions link to addresses, not names. With sufficient transaction history, on-chain analysis firms can often connect addresses to real identities, particularly when those addresses interact with KYC-verified exchanges. When reviewing withdrawal patterns at Blofin, address clustering is visible in aggregate data, which is precisely why address reuse hygiene matters.
KYC (Know Your Customer): KYC refers to identity verification requirements that regulated financial institutions, including crypto exchanges in most jurisdictions, must enforce. When you buy bitcoin with fiat on a compliant exchange, expect to submit government-issued identification. This permanently links your verified identity to any bitcoin addresses you withdraw to. The broader regulatory context is in KYC and AML explained.
On-chain analysis: On-chain analysis examines Bitcoin's public transaction data to trace fund flows, cluster addresses belonging to the same entity, and sometimes de-anonymize users. Firms like Chainalysis and Elliptic specialize in this, primarily for law enforcement and compliance. Assume that sophisticated observers can cluster your transaction history if you reuse addresses or interact with KYC-verified services without privacy precautions.
Address reuse: Receiving bitcoin to the same address multiple times is address reuse. Each additional use makes it easier for on-chain analysis tools to build a unified spending profile around that address. Generate a fresh address for each incoming payment, good wallet software does this automatically through HD (hierarchical deterministic) key derivation.
Phishing, fake support, and seed phrase scams: Phishing attacks mimic legitimate services, such as exchange login pages, wallet support interfaces, to steal your credentials or seed phrase. Warning signs: the "support" contacts you first, urgency ("your account will be locked in 24 hours"), requests for your seed phrase or private key, and promises that require an upfront payment to unlock winnings. Legitimate services never ask for your seed phrase under any circumstances. Common scam patterns and how to recognize them are documented in common Bitcoin scams.
Rug pull and airdrop scams: A rug pull occurs when project developers abandon a project after collecting funds, leaving participants holding worthless assets. An airdrop scam promises free tokens but requires connecting your wallet or sending bitcoin first, the "send X, receive 2X" structure is a pure scam with no exceptions. Bitcoin users encounter these more in adjacent crypto markets, but recognizing the patterns protects you across the board.
What does Lightning Network vocabulary mean?
The Lightning Network is Bitcoin's layer-2 payment protocol for fast, low-fee transactions. Its terminology differs from on-chain Bitcoin concepts because it operates through a separate protocol layer.
Lightning Network: The Lightning Network routes instant payments through a network of pre-funded payment channels, settling off-chain with near-zero fees. Final settlement happens on the Bitcoin blockchain when channels close. Lightning is designed for small, frequent payments where on-chain confirmation time and fees would be impractical, point-of-sale purchases, micropayments, streaming payments. For a complete explanation of how it functions, see what is the Lightning Network.
Payment channel: A channel is a two-party funding agreement opened with an on-chain Bitcoin transaction. Once open, both parties can send unlimited payments back and forth instantly without touching the blockchain, updating a shared balance. When they close the channel, the final balance settles on-chain as one transaction.
Channel balance and liquidity: Each participant's balance within a channel determines how much they can send. If your outbound balance is low or zero, you cannot initiate payments in that direction. Liquidity describes available capacity in channels along potential payment routes. Insufficient liquidity on all available paths causes payment failures.
Routing: Most Lightning payments route through intermediate nodes rather than traveling directly from sender to recipient. Each intermediate node maintains channels with both sides and earns a small routing fee. If no viable route exists, meaning no chain of nodes with sufficient outbound liquidity connects sender to recipient, the payment fails and must be retried or sent on-chain.
Lightning invoice (BOLT-11): A Lightning invoice is a payment request encoding the amount, destination, and expiration time, formatted per the BOLT-11 specification. The payer scans or pastes the invoice; their wallet finds a route automatically. Invoices expire, typically within one hour, and cannot be reused for subsequent identical payments.
On-chain fees vs Lightning fees: On-chain transaction fees fluctuate with mempool demand, sometimes exceeding 100+ sat/vB during peak congestion. Lightning fees are typically fractions of a satoshi per hop, negligible for small amounts. The tradeoff: opening and closing Lightning channels each requires an on-chain transaction, so Lightning economics favor users who transact frequently enough to amortize those channel open and close costs.
What do market and ownership terms mean?
This section covers the language of Bitcoin markets and ownership, without providing trading or investment advice.
Buy, sell, hold, HODL: Buying bitcoin means exchanging fiat currency for BTC. Selling means the reverse. Holding means maintaining a BTC position without selling. "HODL" originated from a typo in a 2013 Bitcointalk forum post ("I AM HODLING") during a price crash, becoming community slang for holding through volatility rather than panic-selling. It has now also become a backronym for "Hold On for Dear Life", which represents a long-term, "buy and hold" investment strategy, particularly during downturns.
Spot purchase vs limit order: A spot purchase buys bitcoin at the current market price immediately. A limit order sets a target price, your order executes only if the market reaches it. Spot is simpler; limit orders give price control at the cost of uncertain execution timing. Before making your first purchase, see how to buy bitcoin safely.
Market cap: Market capitalization is the current bitcoin price multiplied by circulating supply. As of May 6, 2026, Bitcoin's market cap is approximately $1.62 trillion, based on a price of ~$81,395 and ~20.02 million BTC in circulation (source: CoinMarketCap). Market cap is commonly used to compare Bitcoin's scale against other assets, though it is an imperfect metric, it assumes all circulating BTC could trade at the current marginal price simultaneously.
Volatility: Bitcoin price has historically experienced drawdowns of 50–80% from peak prices during market cycles, as well as periods of rapid appreciation. Volatility is a characteristic of Bitcoin's current price-discovery phase. No glossary can predict future price movements.
Liquidity and slippage: Liquidity measures how easily you can buy or sell without moving the market price. High liquidity means large orders execute near the quoted price. Slippage is the difference between expected and actual execution price, more pronounced on low-liquidity platforms or during rapid market moves.
What do Bitcoin tax and regulatory terms mean?
A brief reference for legal terminology you will encounter when converting fiat to bitcoin or reporting holdings, not jurisdiction-specific advice.
Capital gains: In most jurisdictions, selling bitcoin at a profit generates a taxable capital gain. Rates and holding-period rules vary by country and change over time. Keep records of acquisition cost and sale price for every transaction. This glossary does not provide tax advice; consult a qualified professional in your jurisdiction.
Cost basis and tax lot: Your cost basis is what you paid for a specific bitcoin amount, including exchange fees. A tax lot is a discrete acquisition at a specific date and price. When you sell, you need to identify which lot you are disposing of to calculate the correct gain or loss. FIFO (First In, First Out), LIFO, and specific-identification methods each produce different outcomes depending on price history and jurisdiction.
AML (Anti-Money Laundering): AML regulations require financial institutions, including crypto exchanges, to monitor transactions for suspicious activity and report it to regulators. AML compliance is why exchanges implement KYC, apply transaction monitoring thresholds, and occasionally restrict accounts pending investigation.
Bitcoin terms A-Z index
All terms are defined in the thematic sections above.
A: Address, AML, Anonymity
B: Bitcoin (BTC), Block, Block header, Block subsidy, Blockchain
C: Capital gains, Change output, Channel, Coinbase transaction, Cold storage, Confirmation, Consensus, Cost basis, CPFP
D: Difficulty, Digital signature, Distributed ledger, Double spend
F: Fee rate (sat/vB), Fork (soft/hard), Full node
G: Genesis block
H: Halving, Hardware wallet, Hash, Hash rate, HODL, Hot wallet
I: Invoice (Lightning)
K: KYC
L: Lightning Network, Limit order, Liquidity
M: Market cap, Mempool, Mining, Multisig
N: Node (full node)
O: On-chain analysis
P: Passphrase, Payment channel, Peer-to-peer, Permissionless, Phishing, Private key, Proof of Work, Public key
R: RBF, Recovery phrase, Routing
S: Satoshi, Seed phrase, Self-custody, SHA-256, Slippage, SPV wallet
T: Transaction, Transaction fee, Trust-minimized
U: UTXO
V: Volatility
W: Wallet
Frequently asked questions about Bitcoin terms
Is Bitcoin the same as blockchain?
No. Bitcoin is a specific protocol and digital asset. Blockchain is a generic data structure used by many systems, including enterprise databases, other cryptocurrency networks, supply chain tools, with very different properties. Bitcoin's blockchain is one particular implementation with defined consensus rules, a 21 million supply cap, a specific transaction format, and a global peer-to-peer network enforcing it. Saying "blockchain" when you mean "Bitcoin" obscures what makes Bitcoin specifically valuable.
Does a bitcoin wallet contain my bitcoin?
Your wallet stores your private key or seed phrase, not the bitcoin itself. Your bitcoin exists as UTXO records on the blockchain. The wallet holds cryptographic credentials that prove you control specific UTXOs and authorize you to spend them. If you lose your key without a backup, the bitcoin remains in the blockchain ledger but becomes permanently inaccessible.
What happens if someone gets my seed phrase?
They gain full, irrevocable control of all bitcoin associated with that seed phrase, instantly and permanently, with no recovery mechanism. There is no support ticket to file, no transaction reversal to request, and no authority to appeal to. Guard your seed phrase as if it represents your entire balance, because it does.
What is the difference between a private key and a seed phrase?
A private key controls a single address. A seed phrase, per the BIP-39 standard, which derives all your private keys (and therefore all associated addresses and balances) from one master secret. It is a hierarchical backup: one phrase regenerates your entire wallet on any compatible software. Most modern wallets use seed phrases rather than exposing individual private keys directly.
How many confirmations does a Bitcoin transaction need?
For small, low-risk transactions, 1–3 confirmations are typically accepted. For high-value transfers, 6 confirmations provide strong protection, each additional confirmation adds exponentially more cost to any reversal attempt. Some exchanges apply their own thresholds: at Blofin, we credit most BTC deposits after 3 confirmations for standard amounts.
Why are Bitcoin fees sometimes high?
Fees rise when demand for block space exceeds supply. Each Bitcoin block can hold roughly 1–4 MB of weight-adjusted transaction data. When the mempool fills beyond one block's capacity, miners prioritize higher-fee-rate transactions. During the 2023 Ordinals inscription surge, fees exceeded 500 sat/vB. During calm periods, fees can drop below 1 sat/vB. Always check a mempool explorer before sending large amounts.
What is a UTXO and why does it affect fees?
A UTXO is an indivisible chunk of bitcoin you received. Spending it consumes the entire UTXO as a transaction input. More inputs means more transaction data and higher fees, since fees scale with weight in virtual bytes. A wallet with 50 small UTXOs may pay 5–10x more in fees than a wallet with a single large UTXO of the same total value. Consolidating small UTXOs during low-fee periods reduces future transaction costs.
What is Replace-By-Fee (RBF)?
RBF lets you re-broadcast your own unconfirmed transaction with a higher fee, replacing it in the mempool to get confirmed faster. The original transaction must have been flagged as RBF-enabled (opt-in RBF per BIP-125) at broadcast time. RBF does not create a new double-spend risk for yourself, it replaces your own stuck transaction with a functionally identical one at a higher fee rate.
What is halving and what does it not guarantee?
A halving cuts the block subsidy in half every 210,000 blocks. The fourth halving at block 840,000 in April 2024 reduced the reward from 6.25 to 3.125 BTC. The next halving at block 1,050,000 will reduce it to 1.5625 BTC, projected for 2028. Halvings reduce new supply issuance and are frequently discussed in the context of price cycles, but past correlations do not guarantee future price behavior, and the relationship between supply changes and price is not deterministic.
When should I use Lightning instead of on-chain Bitcoin?
Use Lightning for small amounts, roughly under $50–100 equivalent, where speed and near-zero fees matter more than maximum settlement security. Use on-chain for large amounts, cold storage transfers, or any situation requiring full blockchain confirmation finality. Lightning channels require on-chain transactions to open and close, making the protocol most economical for users who transact frequently.
Researched and written by the BloFin Academy editorial team with AI-assisted drafting. All facts independently verified.
Disclaimer: This article is for informational purposes only and does not constitute financial advice. Cryptocurrency trading involves substantial risk of loss. Past performance does not guarantee future results. Always conduct your own research and consider your financial situation before trading. BloFin does not guarantee the accuracy of third-party data referenced herein.