Two issues in language development are explored--the emergence of the ability to communicate and the relationship between emerging forms and functions. Solutions to these problems involve the notion of interpretation and depend on the fact that adults interpret children's behaviors as if they were meaningful according to the adult system. The language development of five children between ages 0;1 and 2;6 was investigated. Focus was on these children's emerging ability to converse on different topics in interaction with their mothers. Conclusions are that: (1) children come to communicate because they are interpreted as communicating; (2) for an accurate picture of language development to be achieved, topic types initiated by children must be accounted for; and (3)the emergence of topic types accompanies the emergence of the appropriate communicative behaviors to express these topics. Therefore, in asking whether means of expression or topic type come first, the question of the relationship between emerging forms and functions is raised. A solution to the form/function or expression/topic question points to function preceding form in some cases and form preceding function in others. Adult interpretation of children's communicative behavior is important in both types of development. (JK)