Learn Finnish: Minä en halua sekaantua tähän kiistaan. - I don't want to get involved in this dispute.

In Finnish, verbs of interference, participation, and joining usually require the illative case. The verb sekaantua (to get involved / to interfere) is one of these verbs. You are metaphorically putting yourself into the situation, so you use tähän kiistaan instead of tässä kiistassa.

The lesson mentions osallistua and puuttua. How is sekaantua different from them?

While all three take the illative case, their meanings differ in tone. Osallistua is neutral or positive (to participate / take part). Puuttua means to intervene or address a problem, often with authority. Sekaantua implies meddling, interfering, or getting mixed up in something, often with a negative or messy connotation.

How is the verb sekaantua formed, and what is its root?

It comes from the root seka- (mixed), which you also see in words like sekaisin (mixed up) and sekoittaa (to mix). The -ntua suffix makes it a reflexive or automative verb, meaning the action happens to the subject itself. Thus, it literally translates to getting yourself mixed up in something.

As a quick refresher, how does tämä turn into tähän?