In general, a namespace is an abstract container providing context for the items (names, or technical terms, or words) it holds and allowing disambiguation of homonym items residing in different namespaces.

As a rule, names in a namespace cannot have more than one meaning, that is, its components cannot share the same name. A namespace is also called a context, as the valid meaning of a name can change depending on what namespace applies. Names in it can represent objects as well as concepts, whether it is a natural or ethnic language, a constructed language, the technical terminology of a profession, a dialect, a sociolect, or an artificial language (e.g., a programming language).

For many programming languages, a namespace is a context for identifiers. In an operating system, an example of namespace is a directory. Each name in a directory uniquely identifies one file or subdirectory, but (through hard links) one file may have multiple names. In the Java programming language, items that appear in namespaces have a short (local) name and unique long "qualified" names for use outside the name space. Also, some compilers (for languages such as C++) combine namespaces and names in a process called name mangling.

Below is an example of a namespace in C++:

namespace Box1{
int boxSide = 4;
}
namespace Box2{
int boxSide = 12;
}
int main () {
cout << Box1::boxSide << endl; //output 4
cout << Box2::boxSide << endl; //output 12
return 0;
}