Learn Romanian: Acel pui este mic. - That chicken is small.

We use acel (that) right before a noun, like in acel pui. If you wanted to use acela, it usually stands alone to mean "that one", or it goes after the noun with a "the" attached to it, like puiul acela (that chicken).

Does pui refer to the animal or the food?

It can be both! Pui is used for chicken meat you eat, but it also means a baby animal, specifically a chick. If you want to talk about an adult female chicken (a hen) on a farm, you would usually say găină.

If I wanted to say "Those chickens are small," how does the word pui change?

The word pui actually doesn't change at all! It is one of the few Romanian nouns that is exactly the same in singular and plural. You say un pui for one chicken and doi pui for two chickens. The rest of the sentence would change around it: Acei pui sunt mici.

Why is the word for small mic instead of mică?

In Romanian, describing words (adjectives) have to match the gender of the noun. Because pui is a masculine word, we use the masculine form mic. If we were talking about a feminine animal, like a cat (pisică), we would use the feminine form mică.