Application Programming Interface (API)

An application programming interface (API) is a source code interface that an operating system or library provides to support requests for services to be made of it by computer programs.
See more at Wikipedia.org...

Application Programming Interface is a set of functions that conform to conventions of a particular operating system (e.g., Windows) which allows the user to programmatically access the functionality of another program. For example, the kernel of STATISTICA Neural Networks can by accessed by other programs packages (e.g., Visual Basic, STATISTICA BASIC, Delphi, C, C++) in a variety of ways.