> - Oes rheol i esbonio pryd mae rhywun yn defnyddio "rydych" neu "ydych" >wedi geiriau fel "sut", "pwy", ble", ac ati? Oes, yn wir, ond fedra i ddim ei esbonio'n dda yn y Gymraeg o achos diffyg fy ngwybodaeth am y termau technegol gramadegol cywir Cymraeg. You use 'rydych' when 'chi' is the subject of the question or phrase to which it belongs and is not in the copula associated with (i.e., in apposition to) a question word. For many question words, this means you automatically use 'rydych' since the question words are not nominal, and therefore the question is not copular: Sut rydych chi? Pam rydych chi'n bod mor wirion? Ble rydych chi'n cael eich parti pen blwydd? Pryd rydych chi'n cael eich parti pen blwydd? So that leaves 'beth' and 'pwy'. Examples where 'beth' and 'pwy' are not in apposition to 'chi' are Beth rydych chi'n (ei) wneud? Pwy rydych chi'n dweud eich bod wedi (ei) weld? In both cases, the question word is in apposition to the implied (ei), or to put it a different way, 'chi' is the subject of a different phrase: 'gwneud' or 'gweld'. You only use 'ydych' when the question word is in apposition to 'chi': Pwy ydych chi? Beth ydych chi? Hwyl. --Mark