Young children who hear more child-directed speech (CDS) tend to have larger vocabularies later in childhood (e.g., Ramirez-Esparza, Garcia-Sierra, & Kuhl, 2014; Weisleder & Fernald, 2013), but the specific structural characteristics of CDS underlying this link have previously been underspecified. The present studies sought to elucidate how three structural features of parents' language input -- the use of word repetition, isolated words, and discourse continuity -- support children's language learning. In previous research, I showed that repetition of object labels in successive sentences promotes young children's encoding of new words (Schwab & Lew-Williams, 2016a). Here, Chapter II examines the extent to which parents' repetition relates to children's learning at different time points in development. Next, Chapter III examines how parents' use of isolated words interacts with repetition in promoting children's learning of new words. Finally, Chapter IV investigates how continuity of reference promotes children's learning. Collectively, these studies reveal that the packaging of information within child-directed speech influences children's word learning, although the extent to which each structure matters depends on children's level of language knowledge.