Definition
A blockchain is an ordered record replicated across participants. Blocks refer to earlier history through cryptographic hashes, while participants check updates under the network's validation and consensus rules. Ethereum's introduction explains this shared record and block linkage; different networks choose different consensus mechanisms.
Broadcasting is not inclusion
A transaction being sent to a network does not itself put it into a block. The Bitcoin white paper, especially its network and verification sections, distinguishes broadcasting, block acceptance and further confirmation. Its proof-of-work description is not Ethereum's current proof-of-stake mechanism.
The word blockchain does not promise that any request will be included, that execution will succeed or that a receiving company will immediately credit an account. Those are separate questions.
Inclusion is not finality
Finality concerns the accepted history becoming resistant to reversal under the particular consensus rules. In proof-of-stake Ethereum, Gasper distinguishes justified and finalized checkpoints. Reversing finalized history would require a critical consensus failure. This is not an unconditional guarantee after a fixed number of minutes, and it is not one finality model for every blockchain.
For the everyday account model, read Bitcoin explained or Ethereum explained. For a payment still showing pending, use the Ethereum transaction diagnosis rather than treating the word blockchain as confirmation of a transfer.
Often confused with
A blockchain is not automatically private, fast, decentralized in every operational layer, or a good replacement for every database. A wallet's balance view and an exchange's account ledger are not simply alternative names for the network's accepted history.
Sources
Sources checked 5 October 2026; protocol examples are identified rather than generalized to every network.
- Bitcoin white paper — broadcast, network acceptance and proof-of-work confirmation.
- Ethereum.org: Introduction — replicated record, block references and current Ethereum context.
- Ethereum.org: Gasper — Ethereum checkpoint finality and its consensus-failure boundary.
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