Learn Swedish: Mössen bor i ett litet hål under golvet. - The mice live in a small hole under the floor.

Mus is an irregular noun that changes its main vowel in the plural (this is called vowel mutation or omljud). The u mutates into an ö, and we add an extra s to keep the vowel sound short, making the plural möss (mice). To say 'the mice', we just add the definite plural ending -en to get mössen.

Why do we use litet instead of liten for 'small'?

Because hål (hole) is an ett word (ett hål). In Swedish, adjectives must match the gender of the noun they describe. The word for 'small' is slightly irregular: it is liten for en words, but it changes to litet when describing ett words.

If ett hål is one hole, what is the plural for 'holes'?

It stays exactly the same! Because hål is an ett word that ends in a consonant, it does not take any ending in the indefinite plural. So, 'a hole' is ett hål, and 'two holes' is simply två hål.

Can you use bor (live) for animals, just like for humans?