The Common Language Infrastructure (CLI) is an open specification (published under ECMA-335 and ISO/IEC 23271) developed by Microsoft that describes the executable code and runtime environment that form the core of the Microsoft .NET Framework and the free and open source implementations Mono and Portable.NET. The specification defines an environment that allows multiple high-level languages to be used on different computer platforms without being rewritten for specific architectures.
Common Language Interface
The .NET architecture lets you connect together code from different programming languages. I call these "common elements", because the names of these all have the word "common" in them. In this context, common means standard. Common Language Interface describes — Standard linkage between classes, methods, interfaces, enumerations, and other programming elements of .NET.