Learn Finnish: Tämä koppi on liian pieni.

A koppi is usually a very small, functional, and often box-like structure, such as a booth, a kennel, or a tiny shed. A cottage or recreational cabin where people actually stay would instead be a mökki. Translating koppi as "hut" here implies a very cramped, basic, or enclosed space.

How can we use the word koppi to practice the rules for compound nouns from this lesson?

The word koppi is frequently the second part (the head) of a compound noun. To say "a wooden hut", you use the nominative for the first word because it describes the material: puukoppi. To say "a doghouse" (a hut intended for a dog), you use the genitive for the first word to show its purpose or target: koirankoppi.

Does the adverb liian require the adjective pieni to be in the partitive case?

No, liian (too / excessively) is an invariable adverb that does not force the following adjective into the partitive. The adjective pieni remains in the nominative case here so that it agrees with the subject of the sentence, tämä koppi.

Could I use se instead of tämä in this sentence?

Using se (it / that) would change the meaning slightly to "That hut is too small" or "The hut is too small," often implying it was mentioned previously. Tämä (this) emphasizes physical proximity, suggesting the speaker is right next to or inside the hut while complaining about its size.