This fourth volume contains sixteen pepers that look at the development of early childhood language. They are presented in three parts: infancy and protolanguage; the transition from child tongue to mother tongue; and early language and learning. The sociolinguistic account of the early development of the mother tongue presented by Professor Halliday is based on his intensive study of the language of one particular child, Nigel, for the period from nine to eighteen months. The complete 'Nigel Transcripts' are included as a CD with this volume.