In cryptography, a nonce is used for securing communication, as it comes in the form of a non-repeated number. On Ethereum and various smart contract platforms, a nonce is used to segregate and sequence transactions. It is an arbitrary number generated only once by a miner when they hash a transaction.
For Ethereum, a nonce plays an important role in keeping transactions streamlined through a proper order. For instance, a wallet on Ethereum can push multiple transactions through without delay. The issue here is that the system must have a way to recognise which transactions to handle first and in an orderly fashion. This is where a nonce comes in: Each transaction is given a nonce that can be recognised to ensure transactions are handled in order.
