Gas
A unit measuring the computational work an Ethereum operation requires, from a simple transfer to a complex contract call.
Gas is how Ethereum prices computation. Every operation, from storing a value to calling another contract, costs a set amount of gas. A plain ETH transfer costs 21,000 gas. A token swap on a decentralized exchange might cost ten times that. The busier the network, the more each unit of gas costs to buy.
The design exists to stop abuse. Because every step has a price, no one can loop a contract forever or spam the network for free — they would run out of funds first. Gas also separates the amount of work, fixed by the code, from the price per unit, set by the market.
Related terms
The total cost to run an Ethereum transaction, found by multiplying the gas used by the price per unit.
GweiA denomination of ether equal to one billionth, used to quote Ethereum gas prices in readable numbers.
Gas LimitThe maximum amount of gas a user allows a transaction to consume before it stops and fails.
Smart ContractSelf-executing code on a blockchain that runs exactly as written when its conditions are met, with no party able to intervene.