A package groups Classifiers and their relationships together, and provides a namespace for them.

All types of UML classifiers can be organized into packages. Packages themselves can be nested – or contained – within other packages. Subsystems and models are special kinds of packages.

The packages can have dependency, generalization, realize, containment, and association relationships. These relationships are usually derived from the relationships between the classes inside those packages.

A package is drawn with a symbol that looks like a folder.