Learn Finnish: Mikä on ravintolan osoite? - What is the restaurant's address?

ravintolan is the genitive form of ravintola (restaurant). By adding the -n to the end, it shows possession. It works exactly like adding an apostrophe and an s ('s) in English, so ravintolan means "the restaurant's".

Why does ravintolan come before osoite?

In Finnish, the possessor (the one who owns or has the thing) usually goes directly before the thing being possessed. This matches the English word order: ravintolan osoite translates exactly to "the restaurant's address".

Why do we use Mikä for "What" instead of Mitä?

We use Mikä because we are asking to identify a specific, whole thing (an address) in its basic dictionary form. You will usually use Mikä on... when asking "What is..." followed by a single, countable noun. Mitä is used for uncountable things, continuous actions, or partial amounts.

Do we need to change any letters inside ravintola before adding the -n ending?

Not in this case! While many Finnish words have inner letters that change when you add an ending (a rule called consonant gradation), the word ravintola does not contain any of the changing consonants (like k, p, or t) in a place that would be affected. You just stick the -n right on the end.