This is a full-length study of a Celtic language from the standpoint of modern linguistic theory. Dr Awbery particularly discusses a topic - the passive form of the verb - which has itself been of central interest in previous work on transformational grammar. She is thus able to test certain tenets of transformational theory against data from a previously unconsidered language. The results are significant, and argue clearly for a separation of syntactic and semantic analysis; constructions which are related syntactically are shown to have no necessary semantic relation, and the type of description which can reveal one set of relationships is not able to reveal the other. The book is therefore a contribution both to linguistic theory and to the study of the Welsh language. Each step in the argument is carefully explained and documented, and no prior knowledge of Welsh is assumed.