(1) To be logical one must acquire the habit of accurate definition.
This topic ought to appeal strongly to the school teacher, who should above all others make his work stand for clearness, pointedness and continuity.
(2) A predicable is a term which can be affirmed or predicated of any subject.
The five predicables are Genus, Species, Differentia, Property and Accident.
(1) A Genus is a term which stands for two or more subordinate classes.
(2) A Species is a term which represents one of the subordinate classes.
The proximate genus of a species is the next class above the species, while the summum genus is the highest possible class in any graded series of terms. The lowest class is the infima species of that series. The lowest class may be individual.
In natural history genus and species are not relative terms, but absolute, having a fixed place in the series of gradations.
The term genus possesses a double meaning: it may be used to represent objects (extensionally) or qualities (intensionally).
(3) The differentia is that attribute which distinguishes a given species from all the other species of the genus.