1. Case, instance, example, illustration suggest the existence or occurrence of a particular thing representative of its type. Case and instance are closely allied in meaning, as are example and illustration. Case is a general word, meaning a fact, occurrence, or situation typical of a class: a case of assault and battery. An instance is a concrete factual case which is adduced to explain a general idea: an instance of a brawl in which an assault occurred. An example is one typical case, usually from many similar ones, used to make clear or explain the working of a principle (what may be expected of any others of the group): This boy is an example of the effect of strict discipline. An illustration exemplifies a theory or principle similarly, except that the choice may be purely hypothetical: The work of Seeing Eye dogs is an illustration of what is thought to be intelligence in animals.

Did you mean bases?