Learn Swedish: Du ska fasta i tolv timmar innan vi opererar dig. - You will fast for twelve hours before we operate on you.

In strict, formal Swedish grammar, innan is a conjunction used to introduce a full clause with a subject and a verb, just like vi opererar dig here. före is a preposition used before noun phrases, so you would say före operationen (before the surgery). While native speakers often mix these in everyday speech, this lesson focuses on the formal distinction.

Why is the preposition i used instead of för to express the duration of twelve hours?

To express the duration of an ongoing action (how long something lasts), Swedish uses i. English speakers are often tempted to use för because it sounds similar, but in Swedish time expressions, för is usually paired with sedan to mean ago, as in för tolv timmar sedan (twelve hours ago).

Why is the present tense opererar used when the operation is clearly in the future?

In Swedish subordinate clauses dealing with time (started by conjunctions like innan, när, or tills), the present tense is standardly used to talk about the future.

Could I say kommer att fasta instead of ska fasta?