Learn Finnish: Hän laulaa lauluja apinoille. - He sings songs to the monkeys.

The basic word is apina (monkey). Because we are talking about multiple monkeys, we add the plural marker i. For words ending in a, the a changes to o before the plural i, creating the plural stem apinoi-. Finally, we add the allative ending -lle (to/onto) to get apinoille (to the monkeys).

Why is lauluja in the partitive plural instead of the basic plural laulut?

The object of the verb laulaa (to sing) is usually in the partitive case because singing is an ongoing action. Using the partitive plural lauluja means he is singing an unspecified number of songs rather than a specific, finished set of songs.

Why doesn't the verb laulaa change to a plural form since there are multiple monkeys and multiple songs?

The verb in a Finnish sentence only changes to match the subject doing the action. The subject here is hän (he/she), which is just one person. Therefore, the verb takes the singular form laulaa regardless of how many songs or monkeys are involved.

Are the words laulaa and lauluja related?