"He does not want wine."

Translation: Dydy e ddim eisiau gwin.

[Willowfae]

Why is it dydy e and not mae e?

[mizinamo]

Because it's a negative sentence.

"to be" (bod) in negative sentences usually starts with a d- (all that's left of a negative particle nid in earlier forms of the language), though sometimes you can't even see that (e.g. you might see both dydw i ddim... and the shorter dw i ddim...).

[areddragon]

As a side note, nid is still used in (written/non-colloquial) Welsh in some contexts, such as nid arnoch chi mae'r bai (you are not to blame).

[StephenDunscombe]

"Dyw o"? I know the north/south divide is an oversimplification, but I thought "Dyw" was more of a southern thing an "o" more of a northern thing?