Having power to determine, fix, or decide; tending or serving to shape or direct; conclusive.Of use in ascertaining the species; serving to determine the precise kind of a thing: as, determinative tables in the natural sciences (that is, tables arranged for determining the specific character of minerals, plants, etc., and to assist in assigning them to their species); determinative signs in hieroglyphics; determinative ornaments or structures.n. That which determines or indicates the character or quality of something else.n. In grammar, a determinative or demonstrative word.