"Yes, these are tasty potatoes."
Translation:Так, це смачна картопля.
Is there a rule to determine what nouns are countable and not-countable in Ukrainian?
Don't think so. Moreover some of them act as singular and other as plural :/
Mostly nouns that are uncountable in English are also uncountable in Ukrainian. But we also have, for example, a set of mass nouns for veggies: картопля, морква, цибуля, which you use to refer to these veggies in general. There's also countable forms for them: картоплина - картоплини, морквина - морквини, цибулина - цибулини.
Oh, and there's also полуниця: it's both a singular for strawberry and a mass noun for strawberries :) (actually the same goes for other berries as well)
I'm afraid no such rule exists, one can speak of some patterns at most. As for foodstuffs, very many such nouns are uncountable with rare exceptions. These are:
- those consisting of smaller particles like peas (горох), beans (квасоля), peanuts (арахіс)
- greens like onions (цибуля), cabbage (капуста), dill (укроп)
It seems a little bit more complicated when it comes to larger-sized vegetables. Морква (carrots), картопля (potatoes) are uncountable, while огірки (cucumbers) and помідори (tomatoes) are countable. Fruits are mostly countable: яблука (apples), ананаси (pineapples), гарбузи (watermelons).
Edit: Oops, I started writing before I saw Vinnfred's answer. I hope my comment is helpful, too :)