This paper explores the relation between the communicative and categorical functions of language and the acquisition of language production. Three major factors in language acquisition are communication, ability for representation and the process of categorization. This paper offers evidence that a sudden and dramatic increase in lexical skill results from a developmental merging of communicative, representational and categorizational abilities. Observations were drawn from a longitudinal investigation of language development in two male children, collected from parental notes and audiotaped and videotaped free play sessions. In the first step in development, the children used words as proper nouns, as labels for stable and important persons or objects in their environment. The utterances were specific and noncategorical, and lacked intercommunicative function. Needs and desires were indicated by nonword sounds. As development progressed, new words were acquired and language expanded in function and content. Lexical items began to signal categories of objects and actions and serve intercommunicative purposes. In a third stage words developed intercommunicative and semantic function, followed by dramatic increases in vocabulary. Not until the communicative and noncommunicative functions are joined will rapid linguistic growth occur. (CHK)