Relationships in class diagrams

In UML, a relationship is a connection between model elements. A UML relationship is a type of model element that adds semantics to a model by defining the structure and behavior between model elements.
UML relationships are grouped into the following categories:
Category Function
Activity edges Represent the flow between activities
Associations Indicate that instances of one model element are connected to instances of another model element
Dependencies Indicate that a change to one model element can affect another model element
Generalizations Indicate that one model element is a specialization of another model element
Realizations Indicate that one model element provides a specification that another model element implements
Transitions Represent changes in state
You can set properties and use keywords to create variations of these relationships.

Relationships in class diagrams show the interaction between classes and classifiers. Such relationships indicate the classifiers that are associated with each other, those that are generalizations and realizations, and those that have dependencies on other classes and classifiers.

The following topics describe the relationships that you can use in class diagrams: