Define namespace in C++.

Namespaces enable us to organize named items that would otherwise have global scope into smaller scopes, allowing us to give them namespace scope. This permits program parts to be organized into distinct logical scopes with names. The namespace provides a place to define or declare identifiers such as variables, methods, and classes.

Or we could say that A namespace is a declarative zone that gives the identifiers (names of types, functions, variables, and so on) within it a scope. Namespaces are used to arrange code into logical categories and to avoid name clashes, which might happen when you have many libraries in your code base.