Not sure what context this would be used in - does it suggest 'that's all there is'?
This expression is referring to an object in sight, another translation would be 'is that it?'
Your suggestion, 'that's all there is?' would be 'dyna'r cyfan(cwbl) sy 'na?
This expression is referring to an object in sight
Hynny refers to something abstract, not concrete. It could refer to a situation or concept, but you can't refer to an object in sight and call it hynny - that would either be hwnna or honna or something similar.
"That is it" would be a statement not a question. "Is that it?" is the proper English
hynny refers to something indefinite (or plural, too). There are other words used in this context for people or things with definite grammatical genders:
- honno - that one (feminine)
- hwnna - that one (masculine)
honno - that one (feminine)
hwnna - that one (masculine)
You probably want to learn either honna (f) and hwnna (m) or alternatively honno (f) and hwnnw (m) rather than a mix of both. Or just learn them all!