In speaking a child sometimes makes constructions in which a sequence of separate utterances expresses a semantic relation not expressed by either utterance. These "vertical constructions" are the main point of this study. Previous studies of construction in child language have largely dealt with sentences. In this study, sentences are called "horizontal constructions" to distinguish them from vertical constructions and to point up the constructional nature of senquences which are not sentences but, rather, discourses, i.e., vertical constructions. The importance of vertical construction is demonstrated on the grounds that these constructions are the developmental basis for horizontal constructions. Once horizontal constructions are developed, vertical construction continues as an active process, resulting in more complex constructions. The second point of this study is methodological. Despite the importance of vertical construction in the development of language, investigators have not discussed this phenomenon because their research has been limited to the study of phonology or sentences. This study, by including one-word utterances, repetitions, unintelligible utterances and discourses, points out the developmental continuity from early conversation to later sentences and proposes that language is learned, primarily in the communicative interactions between the child and other speakers in the speech community. (Author/CLK)