GENUS, among metaphysicians and logicians, denotes a number of beings, which agree in certain general properties common to them all; so that a genus is nothing else but an abstract idea, expressed by some general name or term.
It is plain, therefore, that by a genus we do not barely signify one particular thing, nor yet a plurality of things; but a sort or kind of things, all agreeing in certain general properties.
Thus animal is said to be a genus in respect of man and brute, in regard man and brute agree in the common nature and character of animal: so a right-lined figure of four sides, is a genus in respect of a parallelogram, and a trapezium; and so likewise is substance,
in respect of substance extended which is body, and thinking substance which is mind.