This book is a comprehensive study of the passage from first words to grammar in a sample of children large enough to permit systematic analysis of individual differences in style and rate of development. The authors provide a large body of information about first words and early grammatical development in qualitative and quantitative patterns that are useful not only for researchers in the field, but for speech/language pathologists and early childhood educators interested in the assessment of early language. The results support a unified functionalist approach to language development, and have implications for the way we think about the structure and breakdown of language under normal and abnormal conditions.