What is one way that countable and uncountable (count and non-count) nouns differ?

We use many/few for countable nouns and much/little for uncountable nouns.

Use many and few with countables. I have many candles. I have few flashlights.

Use much and little with uncountable nouns. That room has much light. But this one has little.

Uncountable nouns take the singular. Peace is ... Hope is ... Light is ...

A noun can be countable even if no one can count it! The many grains of sand ... The many water molecules in the ocean ...