Learn Swedish: Varför måste bromsen bytas? - Why must the brake be replaced?

In Swedish, you don't need a separate word for 'be' when using the s-passive with a modal verb. The -s added to the end of the active infinitive byta (to replace) turns it into bytas (to be replaced). So, the combination måste ... bytas translates directly to 'must ... be replaced'.

How do I know to use bytas instead of just byta?

The sentence is in the passive voice, meaning the subject (bromsen, the brake) is having an action done to it rather than doing the action itself. Because it comes after the modal verb måste, you take the base infinitive form byta and simply add an -s to make it a passive infinitive: bytas.

Why does the verb måste come before the subject bromsen?

This is a great time to remember the V2 (verb-second) rule. In a question starting with a question word like Varför, the verb must take the second position in the sentence. Therefore, the modal verb måste comes right after Varför, pushing the subject (bromsen) to the third position.

Could I use ändras here instead of bytas if I want to say the brake must be 'changed'?