Learn Finnish: Tämä kauppa ei myy viiniä. - This store does not sell wine.

In Finnish negative sentences, the negative word (ei) does the heavy lifting by changing to match the subject (minä en, sinä et, se ei). The main verb stays in its plain stem form without any personal endings. The dictionary form here is myydä (to sell). For Type 2 verbs, we drop the -dä to get the stem myy-. Therefore, it becomes simply ei myy.

Why does the word for wine end in -ä (viiniä)?

Viiniä is in the partitive case. In Finnish, if a sentence is negative, the object of the sentence usually has to be in the partitive case. Even in a positive sentence (This store sells wine), it would take the partitive because wine is an uncountable liquid. We form it here by adding -ä to the basic form viini.

Why do we add -ä instead of -a to make viiniä?

This is because of vowel harmony. The word viini only contains the vowel i. In Finnish, the vowels i and e are neutral, but when a word only contains these neutral vowels, it pairs with front vowel endings (-ä, -y, -ö). Therefore, we use -ä instead of -a.

Why isn't kauppa in the partitive case as well?