Questions & Answers about Ovatko he torilla vai kadulla?
Why use the -lla ending for "at the market square" and "on the street"?
The ending -lla (the adessive case) is used for external locations, usually translating to "on" or "at". Open outdoor spaces like a market square (tori) or a street (katu) are conceptually treated as surfaces you are "on", so they take -lla rather than the "inside" ending -ssa.
The dictionary word for street is katu. Why does it change to kadu- in kadulla?
This happens because of a spelling rule called consonant gradation. When you add a closed ending like -lla to certain words, a single t in the final syllable softens to a d. Therefore, katu changes its stem to kadu- before taking the ending.
Why do we use -lla instead of -llä here?
This is due to vowel harmony. Because the words tori and katu contain back vowels (o and a, plus u), their endings must also use the back vowel a. If the word had front vowels like ä or ö, you would use -llä.
Why use vai for "or"? Could I use tai instead?
In Finnish, vai is used specifically for questions where the listener must pick between mutually exclusive options (either they are at the market, OR they are on the street). Tai is used in regular statements or when options are open-ended.