Questions & Answers about Lapsen takia hän jää kotiin.
Why is 'lapsi' (child) written as lapsen here?
The word takia is a postposition meaning 'because of'. In Finnish, most postpositions require the noun coming right before them to be in the genitive case (the 'possessive' case ending in -n). So lapsi becomes lapsen. You can think of it literally as 'the child's because-of'.
The English translation says 'stays at home'. Why use kotiin (into home) instead of kotona (at home)?
This is a very common Finnish quirk! The verb jäädä (to stay) requires the location word to be in a 'destination' case (like the illative case, meaning 'into'). Finns think of staying as an action directed into a place rather than just existing there. So, you must say jää kotiin ('stays into home') rather than using the static location word kotona.
Could I change the word order and say 'Hän jää kotiin lapsen takia'?
Yes, you can! Finnish word order is quite flexible. By moving Lapsen takia to the beginning of the sentence, the speaker is just emphasizing the reason. It highlights that it is specifically because of the child that he is staying home.
How do we know hän means 'he' here and not 'she'?
We actually don't know for sure just from this sentence! The Finnish pronoun hän is gender-neutral and means both 'he' and 'she'. The translation says 'he' here, but depending on the broader context of a real conversation, it could just as easily mean 'Because of the child she stays at home.'