Experiments conducted to find ways of teaching two and three year olds mathematical concepts were found to have general implications for concept learning. The failure of an initial attempt to teach the concepts "fat" and "skinny" led to a design of instructional procedures that would utilize a concept's name while trying to teach its semantic content. A study of variant procedures used to teach the concept "round" emphasized the importance of verbal representation, and a final experiment, designed to teach "square," was performed to determine whether linguistic or concrete referential contexts were more important. The results supported the linguistic approach to semantics rather than the psychological: the relation of words to other words appears more crucial than the relation of words to things. Preschool instructional approaches should consider the communicative context of experiences as well as children's direct experience with materials. (DR)