A namespace is an abstract container that provides context for the items it holds and disambiguation of items having the same name but residing in different namespaces.

Names in a namespace cannot have more than one meaning: two or more things within a namespace cannot share the same name. A namespace is referred to as a context, as the meaning of a name can change depending on the namespace applied to it.

In many programming languages, a namespace is a context for identifiers. In an operating system, an example of namespace is a directory. It contains items that must have unique names. In the Java programming language, items that appear in namespaces have short local names and unique long qualified names for use outside the namespace.