The topic of variation in language has received considerable attention in the field of general linguistics in recent years. This includes research on linguistic micro-variation that is dependent on fine distinctions in syntax and information structure. However, relatively little work has been done on how this variation is acquired. This book focuses on how different types of variation are expressed in the input and how this is acquired by young children. The collection of papers includes studies of the acquisition of variation in a number of different languages, including English, German, Greek, Italian, Korean, Norwegian, Swiss German, Ukrainian, and American Sign Language. Different kinds of linguistic variation are considered, ranging from pure word order variation to optionally doubly filled COMPs and the resolution of scopal ambiguities. In addition, papers in the volume deal with the extreme case of variation found in bilingual acquisition.