Learn Finnish: Me siivoamme keittiön tiistaina. - We clean the kitchen on Tuesday.

The base word for Tuesday is tiistai. To say "on Tuesday", Finnish adds the ending -na (or -nä depending on vowel harmony). This ending is called the essive case, and it is the standard way to express happening "on a specific day of the week".

Why isn't tiistaina capitalized?

Unlike in English, days of the week (like tiistai) and months of the year are always written in lowercase in Finnish, unless they happen to be the very first word in the sentence.

Where does the word siivoamme come from?

It comes from the dictionary verb siivota (to clean). This is a Type 4 verb (verbs ending in -ta or -tä). To make the "we" form, you drop the -ta, add an -a to get the stem siivoa-, and finally add the personal ending for "we", which is -mme.

Why is there an -n at the end of keittiön?

The -n ending marks the object of the action. Because we are cleaning the entire kitchen (a complete, finished action), we use this -n ending (the accusative/genitive case). If we were just tidying up a bit of the kitchen without finishing it entirely, we would use the partitive case instead (keittiötä).