Learn Finnish: Kuumimmassa autiomaassa selviytyy vain vahvin eläin. - Only the strongest animal survives in the hottest desert.

To add a case ending to a superlative, you first need its stem. For kuumin, the strong stem is kuumimpa-. Because the inessive ending -ssa (in) closes the syllable, consonant gradation kicks in and changes the strong -mp- to a weak -mm-. This creates the weak stem kuumimma-, to which we attach the ending to get kuumimmassa.

Why is vahvin (strongest) not using the -impa- or -imma- stem like kuumimmassa does?

Because vahvin is the subject of the sentence (the strongest animal), it stays in the basic dictionary form (nominative case). The -impa- and -imma- stems are only needed when you have to attach other case endings to the adjective.

The verb selviytyä (to survive) often requires the elative case (-sta). Why is autiomaassa in the inessive case (-ssa) here?

It depends on the context! If you survive a specific event, danger, or ordeal (like an illness or a car crash), selviytyä takes the elative because you are surviving "out of" it. However, in this sentence, the desert is simply the physical environment where the animal lives, so we use the location-based inessive case -ssa (in).

What parts make up the word autiomaassa?