"Do you want a new shirt?"
Translation:Dych chi eisiau crys newydd?
'Dach chi' is the North Walian equivalent of 'Dych chi'; 'Wyt means the same but is the intimate version used with friends and family. Grammatically 'Wyt ti' is the 2nd person singular while 'Dych/Dach chi' is the 2nd person plural, however 'Dych/Dach chi' is also the polite version you would use with a stranger or in a formal situation.
It's a bit like the tu/vous distinction in French, tu/Vd in Spanish and du/Sie in German. English lost this distinction a while ago when 'thou' fell into disuse.