This chapter focuses on the question of how children learn form–meaning mappings in the development of multiword utterances (i.e. the meaning associated with a specific sentence produced in a specific context). Following a theoretical overview, we examine the relationship between the input children hear and their early sentence productions through the lens of children’s grammatical errors. The goal is to determine the sources of input to which the learner is sensitive in the development of form–meaning mappings, and how these mappings may be refined over the course of development. We then consider how the semantic components of multiword utterances and the pragmatic (information-structural) contexts in which they occur impact on children’s early usage and interpretation of grammatical constructions to understand the cues children use to assign meaning. The chapter ends with a summary of outstanding questions and future directions.