Ethereum glossary

The ABI is a contract's instruction manual: it lists the functions you can call and the data each one expects and returns.

Account abstraction lets a wallet be a programmable contract, with rules such as spending limits, instead of a single key.

An address is the public identifier of a wallet or contract on Ethereum, a long string starting with 0x.

An allowance is the amount of your tokens that an app is permitted to move on your behalf.

An approval is the action of giving an app an allowance, so it can move a set amount of your tokens.

The base fee is the minimum price per unit of gas that the network sets for every transaction in a block.

A block is a batch of transactions added to the blockchain together, roughly every twelve seconds on Ethereum.

A bridge moves value between two blockchains, usually by locking tokens on one chain and issuing matching tokens on the other.

A bundler collects requests from smart accounts and submits them to Ethereum as ordinary transactions.

Decimals tell you how many digits of a token amount sit after the decimal point, because contracts store whole numbers only.

An EIP is a public proposal to improve Ethereum, written in a standard format and discussed openly before adoption.

EIP-712 is a standard for signing structured messages, so your wallet can show readable fields instead of an opaque string.

ENS, the Ethereum Name Service, is a naming system that maps readable names like alice.eth to addresses.

An EOA, or externally owned account, is a regular wallet controlled by a private key rather than by contract code.

An ERC is an application-level Ethereum standard, such as the rules for how tokens behave, so apps can work with them.

ERC-1155 is a token standard that lets a single contract hold many kinds of tokens, both fungible and unique.

ERC-20 is the standard for interchangeable tokens, where every unit is identical, like stablecoins and most governance tokens.

ERC-721 is the standard for NFTs, where each token is unique and has its own owner.

The EVM, or Ethereum Virtual Machine, is the shared engine that runs smart contract code on Ethereum and many other chains.

Gas measures the computing work a transaction needs, and you pay for it in small amounts of ETH.

A gwei is one billionth of an ETH, the everyday unit for quoting gas prices.

In an upgradeable contract, the implementation is the contract holding the actual logic that the proxy forwards calls to.

A layer 2 is a separate chain built on top of Ethereum that processes transactions more cheaply while relying on Ethereum for security.

Mainnet is the live Ethereum network where transactions involve real money, as opposed to test networks.

Metadata is the descriptive data attached to a token, such as its name, image and traits, usually stored outside the chain.

A multisig is a wallet that needs approval from several people before it can move funds.

An NFT is a token that is unique, so it can represent ownership of a single item such as art, a ticket or a name.

An oracle is a service that brings outside information, such as a market price, onto the blockchain for contracts to use.

A paymaster is a contract that pays the gas fee on behalf of a smart account user, sometimes in exchange for another token.

A permit is an approval you grant by signing a message, with no transaction and no gas fee from you.

A price feed is an oracle service that keeps the latest market price of an asset available for contracts to read.

The priority fee is an optional tip you add to a transaction to get it included sooner.

A private key is the secret number that proves you control a wallet, and anyone who has it can spend your funds.

A proxy is a contract at a fixed address that forwards calls to another contract, which lets the logic be upgraded.

A seed phrase is a list of words that can restore your wallet and all its private keys, so it must stay secret.

A signature is proof, made with your private key, that you approved a specific message or transaction.

A smart account is a wallet run by a contract, so it can offer features like recovery, batching and spending rules.

A smart contract is a program stored at an address on the blockchain that anyone can call and that runs exactly as written.

A stablecoin is a token designed to hold a steady value, usually one US dollar.

In a multisig, the threshold is how many of the owners must approve before a transaction goes through.

A token is a digital asset tracked by a smart contract, such as a stablecoin, a game item or a membership pass.

A transaction is a signed instruction that changes something on the blockchain, such as sending ETH or calling a contract.

A wallet is the app or device that holds your keys and lets you sign transactions and view your assets.

A wei is the smallest unit of ETH, one quintillionth of an ETH, and contracts count ETH amounts in it.

WETH is wrapped ether, ETH converted one to one into an ERC-20 token so apps can handle it like any other token.

A wrapped token is a token that stands in for another asset, backed one to one so it can be used where the original cannot.