was born 20 June 1924 in
, a village on the outskirts of Swansea which was at that time largely Welsh-speaking, one of the two sons of
, mine worker, and his wife
. He was educated at Bishop Gore grammar school in
, 1935-1941, and then at
Swansea University College
where he read English, French and Welsh. He took his degree in 1943 before being drafted into the army. He returned to college in 1947 to take a diploma in education but in 1948 he was invited by
, the professor of Welsh, to study for an honours degree in Welsh and he gained his first-class degree the following year. As a research topic for his M.A. degree he chose to study the Welsh dialect of his native area and his dissertation laid the foundations of his deep interest in language throughout his life. He won a University of Wales Fellowship and he continued his studies at the universities of
). In 1952 he was appointed lecturer in the expanding department of Welsh at the University College of Wales, Aberystwyth where he was responsible for introducing new and innovative degree courses in linguistics, historical linguistics and dialectology. From these courses stemmed his pioneering influential, and still valuable, comprehensive introduction to Welsh linguistics, Ieithyddiaeth, agweddau ar astudio iaith (1961). The study of language, and especially dialect studies, were transformed in Welsh colleges and schools through his undergraduate lectures and the groups of researchers that he nurtured. He was promoted to a senior lectureship and readership; he served as acting head of the Welsh department, 1969-70, and Dean of faculty, 1976-78. He spent a term as visiting professor at the Dublin Institute for Advanced Studies in 1971, as visiting professor of Welsh in University College Dublin, in 1980 and in 1981 he was elected to the chair of Welsh at University College Dublin where he remained until his retirement in 1989 and his return to Swansea. He was elected a Member of the Royal Irish Academy (MRIA) and also appointed an honorary Professor in the Welsh department at University College Swansea.
's main interests were in phonology, dialectology, syntax and the historical orthography of Welsh, a field where he published a series of important articles which challenged and revised many long established ideas. He later turned to syntactical issues, e.g. constituent order in the Welsh sentence, and language interference in bilingual situations.
was one of a rare breed of linguistics scholars who was equally at home in studies of Old and Middle Welsh and of modern linguistics. He was a gifted teacher able to elucidate language complexities, orally and in writing, to a variety of audiences. He succeeded in sharing with his students his own enthusiasm for his subject with the result that his views and ideas were given wide circulation by his students and especially his researchers. He was very aware of the standards of contemporary Welsh and of the effects both of bilingualism and of social and political factors on language change and attitudes, areas which he examined not only in his own community but also, as an examiner, in the schools. His linguistic training and his honesty of mind would not allow him to ignore what he observed and some of his comments on the future of the language and on language policies were at times controversial.
had a warm and open personality and this did much to temper the reception of some of his strong political and social views.
in 1955 and they had two sons and a daughter. He died in
4 August 2003 and was cremated in