Breakdown of Zanim wyjdziesz, musisz zgasić światło.
musieć
to have to
wyjść
to go out, to leave
zanim
before
zgasić
to turn off (a light, flame)
Questions & Answers about Zanim wyjdziesz, musisz zgasić światło.
Why does Polish use the future tense wyjdziesz when English uses the present tense "leave"?
In English, we usually use the present tense after "before" even when talking about a future event. Polish is strictly logical here: if the action of leaving happens in the future, you must use the future tense. Because zanim (before) is followed by the regular indicative mood, we just use the normal future tense form wyjdziesz.
Why are both wyjdziesz and zgasić perfective verbs?
Perfective verbs focus on the completion of an action. You are going to completely leave the room, and you need to completely turn off the light. If you used imperfective forms here, it would sound like you need to be in the continuous process of turning off the light while in the continuous process of walking out the door.
Doesn't zgasić mean "to extinguish"? Can I use wyłączyć instead?
Yes, you can absolutely say wyłączyć światło (to turn off the light), and it is perfectly correct. However, because lights historically used to be candles or gas lamps, the verb zgasić (to extinguish) stuck around. It remains a very natural and standard way to talk about turning off lights in Polish.
What case is światło in this sentence?
It is in the accusative case because it is the direct object of the verb zgasić (it is the thing being turned off). Because światło is a neuter noun, its accusative form looks exactly the same as its basic nominative dictionary form.