Understanding the representational, developmental, and processing differences between abstract and concrete words is critical to developing an understanding of word meanings in general. There is a considerable amount of evidence that concreteness represents a fundamental semantic distinction among words. Concreteness invariably emerges as an important variable that differentiates words in large factor analytic studies (DiVesta & Walls, 1970; Paivio, 1968; Rubin, 1980). Yet, most current theories of word meaning do not directly address this basic distinction. A full theory of word meaning must include information regarding how words may differ in their representations, how these differences are acquired developmentally, and how such variations are reflected in verbal processing. The study of concreteness effects should help us move toward this ultimate goal.