You are happy should be “rwyt ti’n hapus”. There are three different forma if each form of “bod”: a question form, a statement form and a negative form. For “ti” that would be Rwyt ti’n hapus. - You are happy. Wyt ti’n hapus? - Are you happy? Dwyt ti ddim yn hapus. - You are not happy.

This is because the common forms of “bod” are actually contractions of longer verb phrases that included additional particles in the beginning to add important information. For example “dwyt ti” comes from “nid ywt ti” (not are you=you are not). “Rwyt ti” is from “yr yd wyt ti” and “Wyt ti?” comes from “A wyt ti?”

The pattern is relatively easy to remember. The positive statement form usually starts with an r, the negative form with a d and the interrogative form without any addition, because the interrogative particle “a” is just dropped.

So you get in present tense:

Rydw i Dydw i Ydw i

Rwyt ti Dwyt ti Wyt ti

Mae o/hi (this is an exception) Dydy o/hi Ydy o/hi

Rydwn ni Dydwn ni Ydwn ni

Rydych chi Dydych chi Ydych chi

Maen nhw (this too is an exeption) Dydyn nhw Ydyn nhw

*mae and maen (older form is maent) actually are no forms of bod but come instead from the same source as yma, meaning “here is”.