Application Programming Interface (API)

An application programming interface is a contract that lets software ask another system, library, or service to do something in a predictable way.

Application Programming Interface (API) is the boundary a piece of software exposes so something else can use it.

An API might be a set of functions in a library, an HTTP endpoint that returns JSON, or a platform command that another tool can call. The shape changes, but the point is the same: callers get a documented way to ask for work and read the result.

Good APIs make the boring details clear. What inputs are allowed? How does authentication work? What comes back when something fails? Can the contract change without breaking every script that depends on it?