In Welsh the verb eisiau, means 'to want' and is different to other verbs. Edrychwch - look at these sentences:

Notice that there isn't an 'n' before the verb eisiau.

You will also hear the word moyn in the south; it is quite probable that your child will pick it up at school. It has the same meaning as eisiau, and is totally acceptable in conversation.

To ask someone what they want we say:
Beth dych chi eisiau? - What do you want?

or, more informally

Beth wyt ti eisiau?

To ask if they want something specific, we say:

To respond, we say ydw - yes, or nac ydw - no. To decline an offer politely, you could say Nac ydw. Dim diolch - no thanks.