Learn Finnish: Vastaus on niissä asiakirjoissa. - The answer is in those documents.

In Finnish, there are two pronouns that translate to those: nuo (for things you are physically pointing at) and ne (for things previously mentioned or abstract). Here, niissä is the inessive (in) form of ne. It is used because the speaker is likely referring to documents discussed earlier, rather than pointing at a physical stack of papers across the room.

Why do both niissä and asiakirjoissa have the same -ssa ending?

This is called case agreement. When a demonstrative pronoun modifies a noun, it must match the noun's case and number. Because asiakirjoissa is in the plural inessive form, the pronoun must also take the plural inessive form, which gives us niissä.

How do you break down the word asiakirjoissa?

It is a compound word built from asia (matter, issue) and kirja (book), which together mean document. To get the form used here, we add the plural marker -i- and the inessive ending -ssa (meaning in).

Could I change the word order to Niissä asiakirjoissa on vastaus?

You could, but it changes the meaning slightly. Finnish uses word order to show whether a noun is definite (the) or indefinite (a). Starting with the subject Vastaus on means The answer is... Starting with the location makes it an existential sentence, which would translate to There is an answer in those documents.