The syntactic properties of the child's language are studied. Within the framework of transformational grammar, the rules of syntax can be divided into three types: base- or phrase-structure rules, transformational rules, and morphological rules. Each of these rules is discussed. It is stated that the one process that appears to characterize each of these syntactic rules (and language acquisition, in general) is that of "gradual differentiation." Implications for the teacher of the study of the child's language acquisition are presented. (Author/LS)