Gwenhwyseg is a Welsh dialect of South East Wales. The name derives from an old term for the inhabitants of the area, y Gwennwys. One of Gwenhwyseg's characteristics is the change in the long a vowel sound of the diphthong äë (IPA [æʌ]) e.g. "y 'Ted' a'r Meb' a'r Ysbryd 'Glên'" instead of "y Tad a'r Mab a'r Ysbryd Glân". The diphthong 'ae' is changed in the same way:
This is a diphthong which varies slightly over the Gwenhwyseg territory and not the same sound; it is also found in words like 'pen', 'pren', 'pert' etc. This does not occur in short monosyllabic words like 'mam' and 'naw' as what happens in some of the dialects of Montgomeryshire. Gwenhwyseg has influenced the English spoken in the area with English speakers using Welsh words and syntax (see Welsh English), e.g. 'What is on her?' (Beth sydd arni?); 'You can count on 'er wen there's taro.