Learn Swedish: Vi måste förstå frågorna. - We must understand the questions.

The basic singular word is en fråga (a question). To make it plural, it becomes frågor (questions). In this lesson, we learn that to say "the questions" (definite plural), we add the suffix -na to that plural form, resulting in frågorna.

Why does the plural of fråga end in -or before we add the -na ending?

There is a handy rule in Swedish: if an en word ends in the letter -a (like en fråga), you usually drop that -a and add -or to make it plural. Once you have frågor, you just attach -na to make it definite.

Why do we use förstå (to understand) instead of the present tense förstår (understands)?

Because it comes right after måste (must). Måste is a helper (modal) verb. Just like in English, when you use a helper verb, the main verb stays in its basic dictionary form (the infinitive). So it is always måste förstå, never måste förstår.

Would måste change if the sentence was "He must understand the questions"?