This article deals with an important question in the area of developmental psycholinguistics. It studies the conditions for a presyntactcic utterance to become a "canonical sentence" or "canonical utterance" at the stage of the two-word combinations. Two main points are highlighted: (1) how a prelinguistic utterance between 9-12 months of age can have a linguistic modality; and (2) how this utterance becomes a syntactic-semantic-prosodic unit when lexicon is being acquired. The focus is put on the importance of prosody and on relations between the different parameters to create the first grammatical networks. Evidence is taken from spontaneous speech recordings of a large population of children both typical and atypical for their language development; auditive, acoustical, and linguistic analyses were carried out on these data. (Contains 45 references.) (Author/VWL)