The acronym CLS stands for Common Language Specification in the world of .NET software development. It is a subset of the common type system and its main function is to establish a standard set of policies to enable language interoperability within the .NET framework. Other functions of the CLS include enabling code reusability, platform independence, and cross-language inheritance.
As an example, because of the CLS .NET framework developers can derive classes or implement interfaces in one supported programming language and use the same classes in another language. For the same reason, it is easy to implement standard functionality across applications with language-agnostic reusable components thanks to the Common Language Specification.