Application Binary Interface

A standardized specification that defines how to interact with a smart contract's functions at the binary level. The ABI describes the contract's function names, input/output parameter types, and encoding formats, allowing external applications (wallets, dApps, scripts) to correctly encode function calls and decode return values. When you interact with a DeFi protocol through a frontend or directly via code, the ABI is what translates human-readable function names into the bytecode the EVM understands.