The chapter starts by presenting a sketch of the phonology of Irish. This covers first the segmental phonology dealing with consonants and then vowels. The importance of the palatalised–non-palatalised distinction in the consonant system is stressed. The phonotactics of Irish are described and the range of possible consonant clusters outlined. Attention is then turned to prosodic aspects of Irish phonology, with a description of both stress and intonation.

Phonological processes such as allophonic variation and sandhi phenomena are also included, and a description of the initial consonant mutation system is given in phonological terms. In all these sections of the chapter, important dialect differences are noted. Following the description of Irish phonology, a review is presented of studies of the acquisition of Irish as a first (or joint first) language. Two diary studies provided some information on order of acquisition of segments and on patterns of simplification. A longitudinal, group study is also reviewed and the results of this add much more to our knowledge of phonological acquisition in Irish. The chapter concludes with a look at the development of new, urban, forms of Irish, and at the need for more research into phonological acquisition norms in Irish.