a class of objects divided into several subordinate species; a class more extensive than a species; a precisely defined and exactly divided class; one of the five predicable conceptions, or sorts of terms.-an assemblage of species, having so many fundamental points of structure in common, that in the judgment of competent scientists, they may receive a common substantive name. a genus is not necessarily the lowest definable group of species, for it may often be divided into several subgenera. in proportion as its definition is exact, it is natural genus; if its definition can not be made clear, it is more or less an artificial genus.