Namespace (also called name scope) is a logical group of the names (i.e., identifiers) used within a program. A developer specifies multiple namespaces as a way to logically group identifiers based on their use. For example, System.Windows and System.Panels are two namespaces each containing types used for for different purposes. The name used for any identifier may only appear once in any namespace. A namespace only contains the name of a type and not the type itself.