This book presents the findings of a case study in bilingual acquisition and explores their implications for theories of first- and second-language acquisition. The authors focus on the emergence of two languages -- Spanish and English -- during one child's second year of life, and examine the process of language learning from the perspectives of phonology, lexicon, syntax, and language choice.The theoretical questions addressed by the authors include whether phonological distinctions can be acquired on acoustic evidence alone; whether lexical acquisition involves an avoidance of synonymy (not necessarily, the authors suggest); whether all words in early two-word utterances can be assigned to lexical categories; and how early children are able to make appropriate language choices. They also consider the implications of their research for bilingual acquisition, including the questions of whether a bilingual child has one or two linguistic systems; the criteria which should be used in identifying one versus two systems; and the most important determinants of language choice -- the identity of the interlocutor, for example, or the location and context of the conversation?This is an original contribution to the field of early bilingual acquisition and to theoretical work in language acquisition. The authors' finely observed results and the implications they draw from them will be of interest to those working in linguistics, psychology, and related fields, both theoretical and applied, concerned to understand the human ability to acquire language and the evolution of a young child's mind.