Metaclass is a profile class and a packageable element which may be extended through one or more stereotypes.

A metaclass may be shown with the optional stereotype «Metaclass» shown above or before its name (all lower-case «metaclass» was used in UML versions prior to 2.4).

Figure 6.4. Metaclass Component [UML-DIAGRAMS.ORG]

Metaclass may be extended by one or more stereotypes using special kind of association: extension.

Figure 6.5. Stereotype Computer extends metaclass Device [UML-DIAGRAMS.ORG]