Learn Croatian: Navijači pjevaju cijelu utakmicu. - The fans sing through the whole match.

In Croatian, you use the accusative case without a preposition to express how long an action lasts. Because the singing lasts for the whole match, the phrase cijela utakmica takes the accusative form cijelu utakmicu.

The translation says 'through the whole match.' Why isn't there a preposition here?

When expressing that something happens for an entire period of time, Croatian often uses the accusative case entirely on its own. Adding a preposition here would sound unnatural. While you can say tijekom utakmice (during the match, using the genitive case), for the phrase 'the whole match', you just use the plain accusative.

Why is the imperfective verb pjevaju used here?

The verb pjevati is imperfective, meaning it describes an ongoing or repeated action. Since the fans are continuously singing over a duration of time rather than completing a single quick action, the imperfective aspect is required.

Where does the word navijači come from?

It comes from the verb navijati, which means to cheer for, root for, or support a team. A navijač is a sports fan or supporter, and navijači is the nominative plural form used here because they are the subject doing the singing.