To be illustrated or exemplified (by).
Something that serves to illustrate or explain a rule.
Something that serves as a pattern of behaviour to be imitated (a good example) or not to be imitated (a bad example).
Something that is representative of all such things in a group.
A person punished as a warning to others.
A parallel or closely similar case, especially when serving as a precedent or model.
An instance (as a problem to be solved) serving to illustrate the rule or precept or to act as an exercise in the application of the rule.