A concrete use case is a particular type of use case that is directly invoked by an actor and achieves a specific goal. It is self-contained and illustrates a complete flow of events. A concrete use case is a specific instance of using a common set of steps referred to as an abstract use case.

An abstract use case is a particular type of use case that is not directly invoked by an actor but is called by another use case. When two or more use cases have a sequence of the same steps, these steps are extracted and put into a common use case. This common, or abstract, use case is then available to be included in any other use case within the system. Abstract use cases eliminate redundancy and promote reuse, a goal of object-oriented systems design.

Because an abstract use case contains only a subset of the steps in a flow of events, it may not make sense as a standalone use case. An abstract use case is included as part of one or more concrete use cases in order to represent a complete flow of events.