Gwenhwyseg or Y Wenhwyseg (also called "Gwentian" in English) is a Welsh dialect of South East Wales.^[1] 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 to a long e e.g. y Ted a'r Meb a'r Ysbryd Glên rather than the standard y Tad, y Mab a'r Ysbryd Glân ("the Father, the Son and the Holy Spirit"). The diphthong ae is changed in the same way:

This is a diphthong which varies in pronunciation over the Gwenhwyseg territory and not realised with same phoneme; it is also found in words like pen, pren, pert, etc. This does not occur in monosyllabic words containing a short a like mam and naw as 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?" reflects Welsh Beth sy' arni hi?.^[2]

Other differences between standard Welsh and Gwenhwyseg are:^[3]

• BBC – De Ddwyrain – Geirfa'r Wenhwyseg
• Gwefan Cymru-Catalonia: Y Wenhwyseg^{[permanent dead link‍]}