Learn Finnish: Mies on kokkina hotellissa. - The man is working as a cook in the hotel.

In Finnish, you don't always need the verb työskennellä (to work) to say someone works in a profession. Using the verb olla (to be) combined with the essive case on the profession is the most common way to say someone is working as or acting as something.

Why is the word for cook written as kokkina instead of just kokki?

Kokkina is in the essive case, which adds the ending -na or -nä to the word. This case is used to express a role, position, or temporary state. Here, it translates perfectly to "as a cook".

How do I know whether to use -na or -nä for the essive ending?

It depends on vowel harmony. Because the word kokki contains the back vowel o, it takes the back vowel ending -na. A word with only front or neutral vowels, like etsivä (detective), would take -nä to become etsivänä.

Why is it hotellissa and not hotellilla?

Hotellissa uses the inessive case ending -ssa, meaning "in" or "inside". When someone works at a hotel, they are typically working inside the building, so Finnish uses this case. Using hotellilla would sound more like they are just spending time around the hotel premises.