# Nonce

> A number used once. In mining it is the value miners search for; in transactions it stops the same one being processed twice.

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

## Definition

Nonce is short for number used once. In proof-of-work mining, it is the value miners change as they search for a block hash that meets the target.

In account-based chains like Ethereum, every transaction from an address has a sequential nonce, which makes sure transactions are processed in order and that the same one cannot be replayed. If a nonce is wrong, the transaction will not even be accepted into the mempool.

## Related terms

- [Mining](https://business.fudfomo.co/glossary/mining): Using computers to add new transactions to a blockchain and earn newly created coins as a reward.
- [Proof of Work](https://business.fudfomo.co/glossary/proof-of-work): A way to secure a blockchain by making computers do a lot of calculation. Used by Bitcoin.
- [Transaction](https://business.fudfomo.co/glossary/transaction): An instruction recorded on a blockchain that moves value or runs a smart contract.
- [Hash](https://business.fudfomo.co/glossary/hash): A short fingerprint of any piece of data, produced by a one-way mathematical function.

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