Navajo has classificatory system for verb stems that classifies objects by their physical characteristics, in addition to describing the movement or state of the object. Two types of prefixes can be distinguished by their different phonological behavior. When available, the use of the correct verbal root is mandatory: apple 1-to 3.OBJ-2.SUBJ-give(SRO).MOM.PERF, apple 1-to 3.OBJ-2.SUBJ-give(PlO1).MOM.PERF, Number marking on nouns occurs only for terms of kinship and age-sex groupings. American Indian people,