Chapter 20

Genus and species have this in common: that they are predicated of the essence of several things; that by nature they are prior to those things that come under them; and that each is a whole something. Distinguishing peculiarities of genus and species are as follow, namely: that the genus is more general than the species; that the species is richer in differences than the genus; that the genus is predicated of the species univocally, whereas the species is not convertible; and that neither is the genus more specific, nor the species most general, nor can that which is most specific be a genus.

See alternate