In short, a use case describes the interaction between an individual and the rest of the world.

This is very useful because often we cannot describe exactly the interaction (at least, not the most interesting ones).

Most important, the model must be set up to describe the operational interaction among those components precisely.

The system of five phases was used for describing interactions and relationships between phenomena.

Officials familiar with those closed sessions described the interaction between the two leaders as gracious but without much warmth.

A simple diagram describing the interaction is shown below.

D and E describe the interaction between charged objects.

The book describes both functional and dysfunctional social interactions.

There is a wealth of oral history that describe interactions between the two group dating back as early as the 6th century.

It describes interactions where the fitness of one species has absolutely no effect whatsoever on that of the other.