Set of routines, protocols, and tools for building software applications.

• API - Webopedia Definition and Links
• Component Extension (CX) API requirements Version 1.0 - (W3C Note as of 2002-01-15) describes requirements for browser plug-ins and an active component architecture for the Web for server and client software
• DirectX - Webopedia Definition and Links
• Open Document Management Association API (ODMA)
• Simple API for CSS (SAC) - (W3C Note as of 2002-01-15) project to develop a common API for the CSS parsers in the W3C
• Simple API for XML (SAX)
• PC Webopaedia - Application Programming Interfaces (APIs) category page