Definition of ``definition''

What constitutes a good definition? In the era that modestly termed itself the ``Enlightenment,'' some thinkers had the bright idea that the best definition of something was the shortest possible phrase that denoted that thing uniquely. This brilliant idea led to

man

1: featherless biped

whale

1: mammiferous animal without hind feet

In fact, the goodness of a definition depends on the context in which it is given: the previous knowledge that is assumed about the term being defined, the related terms from which it must be distinguished, the crucial qualities that need to be understood.