How do you say sit in welsh?

Answer 1

Eistedd (the verb "to sit").

Incidentally, this is the root of the word "Eisteddfod" (a sitting, or session).

As a command, "Sit" would be "Eisteddwch" (polite / plural) or "Eistedda" (familiar / singular).

Answer 2

The Welsh word for "sit" is "eistedd."