Learn Finnish: Lapsi ei katso televisiota. - The child does not watch television.

This is the main rule of your current lesson! Because the sentence is negative (ei katso), the object of the action must be in the partitive case. We add the partitive ending -ta to the base word televisio to show this.

Why is the verb katso instead of katsoo?

In Finnish negative sentences, the main verb drops its personal ending. While a positive sentence uses katsoo (watches), a negative sentence uses the negative word ei (does not) followed by the plain stem of the verb, which is just katso.

Why does televisio get the -ta ending instead of just -a?

Usually, words ending in a single vowel just take -a or -ä in the partitive case. However, some longer loanwords ending in -io, such as televisio and radio, take the -ta ending instead.

If the sentence were positive ("The child watches television"), would we still use televisiota?

Actually, yes! You would say Lapsi katsoo televisiota. Watching television is an ongoing, continuous action, which also requires the partitive case. However, the golden rule to remember for this lesson is that every object in a negative sentence must be partitive, no matter what kind of action it is.