In the investigation of children's vocabulary, little attention has been directed to the identification and description of the characteristics of their semantic competence. The purpose of this study was to develop an instrument which would index the change with age of preferences for different kinds of definitions. Children's semantic competence was considered to result from their organization of semantic relationships for the purpose of ascribing meaning to words. Other investigators (Feifel and Lorge, 1950;Annett, 1959; Bums, 1960) have assigned children's meaning responses to qualitative dimensions on the basis of certain logical and semantic criteria. Such categorization revealed developmental trends in children's verbal behavior. The present study sought a similar end but rather than having the experimenter assign responses to categories the subjects themselves were required to make this decision through a ranking activity.The intimate relation of vocabulary to the thought process has been recognized in the literature for some time, for example, Fischer, 1966;Church, 1961. Word meaning has come to be considered the result of the active encounter of thinking individuals with reality where the organism mediates verbal sensory data in order to ascribe meaning to it. Meaning, therefore, can be considered both a process and a product variable resulting from the organism's behavior in interpreting environmental stimuli.The mediational view of meaning suggests a relatively unique kind of semantic organization underlying each individual's verbal behavior. For purposes of analysis and discussion this organization might be considered to comprise a multidimensional semantic space which serves to process words for the individual. Meaning accrues to a symbol when it is placed in the individual's semantic space and, therefore, depends upon the dimensions which constitute this space. The dimensions, comprised of logico-semantic relations, i.e., the way meanings of words 507