# Transaction

> An instruction recorded on a blockchain that moves value or runs a smart contract.

Canonical URL: https://fudfomo.co/glossary/transaction
Source: What The Block! Dictionary v1.0 (last updated 2026-04-25), browsable at https://wtb.fudfomo.co.

## Definition

A transaction is the basic unit of activity on a blockchain. It is signed by the sender's private key and broadcast to the network, where validators or miners include it in a block.

Transactions can transfer coins, call functions on smart contracts, or both. Once a transaction is included in a confirmed block, it cannot be undone, which is why double-checking before signing matters.

## Related terms

- [Block](https://fudfomo.co/glossary/block): A bundle of transactions added to a blockchain together.
- [Mempool](https://fudfomo.co/glossary/mempool): The waiting area where pending transactions sit before they are included in a block.
- [Gas Fee](https://fudfomo.co/glossary/gas-fee): The cost of getting your transaction included on the blockchain. Goes to the people who run the network.
- [Address](https://fudfomo.co/glossary/address): A short string of characters that identifies a wallet on a blockchain.

## See the full catalogue

What The Block! covers more than 2,000 plain-English crypto terms, delivered as embeddable hover-state tooltips for crypto exchanges. https://wtb.fudfomo.co