Chapter 18

One must know that the five terms have this in common with each other, that they are all predicated of several things. But they differ from one another for the following reason, namely, that: while genus is predicated of the essence of several things differing in species; species is predicated of the sort of several things differing in number; difference and accident are predicated of the sort of several things differing in species; and property is predicated of the sort of several things differing in number, that is, of one species and the individuals contained in it. Moreover, the difference differs from the accident in that, while the difference is essential, that is to say, is a part of the substance of the subject, the accident does not exist as a part of the substance but as a non-essential.

See alternate