yes is translated by oui, except when used in reply to a negative question in which case the translation is si or, more emphatically, mais si: 'did you see him?'—'yes (I did)' = 'est-ce que tu l'as vu?'—'oui (je l'ai vu)'; 'you're not hungry, are you?'—'yes I am' = 'tu n'as pas faim?'—'si (j'ai faim)'.Note that there are no direct equivalents in French for tag questions and short replies such as yes I did, yes I am.For some suggestions on how to translate these, see do.