The signifier implies a symbolic dimension that is not reducible to empirical referents. For inanimate referents, the accusative form is identical to the nominative form. Scheffler contends that Kuhn confuses the meanings of terms such as "mass" with their referents. Word overextension is governed by the perceptual similarities children notice among the different referents. Adjectives modify a noun by providing additional information about their referents. Abstract objects have no physical referents, whereas concrete objects do. The relationship between words and their referents is called semantic. These classifiers are moved through sign space to iconically represent the actions of their referents. An obviative/proximate system has a different way of distinguishing between multiple third-person referents. Researchers typically infer the existence of moods from a variety of behavioral referents (Blechman, 1990). Considerations of references and their referents are sometimes of importance in computing and programming. The main difficulty in understanding native concepts is the uncertainty concerning the referents. "Forms" are ideal in supplying meaning to referents for general terms. All languages are able to specify the quantity of referents. The mapping problem asks how infants correctly learn to attach words to referents.