Learn Hardcore Norwegian: Jeg åpner vinduet siden det er varmt.

siden is a subordinating conjunction meaning “since” in the sense of “because.” It introduces a reason that’s assumed to be known or obvious (“as it’s hot”). fordi also means “because” but is more direct and neutral. Grammatically, both siden and fordi introduce subordinate clauses with subject–verb order (no inversion).

Why is there a det in the clause “siden det er varmt”? Can it be omitted?

In Norwegian you always need a subject in a clause. Here det is a dummy (expletive) subject meaning “it.” You cannot drop it, so siden er varmt would be ungrammatical. Always say siden det er varmt.

Why does the verb in the subordinate clause after siden come after the subject, unlike the V2 rule in the main clause?

Main clauses in Norwegian follow the V2 (verb-second) rule: the finite verb must be in second position (“Jeg åpner vinduet”). Subordinate clauses introduced by conjunctions like siden, fordi or at use subject–verb order (S–V), so you get siden det er varmt.

Why is vinduet in the definite form? Would et vindu ever work?

vinduet means “the window” and is used when both speaker and listener know which window is meant (for example, the window in this room). et vindu (“a window”) could work if you meant any window in general, but if you’re talking about the one you’re actually by, you use the definite form.

Does Norwegian have a continuous tense like English “I am opening”?

No separate continuous tense exists in Norwegian. The simple present (åpner) covers both habitual actions and actions happening right now. If you want to emphasize that you’re in the middle of opening, you can say: • Jeg holder på å åpne vinduet. (I’m in the process of opening the window.)
• Jeg er i ferd med å åpne vinduet. (I’m about to/opening right now.)

Could I have used ettersom instead of siden?

Yes. ettersom also means “because/since” and introduces a subordinate clause with S–V order:
Jeg åpner vinduet ettersom det er varmt.
It’s a bit more formal or literary than siden, but the meaning is the same.

Is there any difference in meaning or register between using siden, fordi, and ettersom?

• fordi: neutral, most common for giving reasons.
• siden: slightly more formal or implies the reason is already known/obvious.
• ettersom: more formal or written style, similar nuance to siden.
All three introduce subordinate clauses with subject–verb order, but your choice affects tone and register.

Why isn’t the verb åpne (infinitive) used instead of åpner?

åpner is the present tense form of åpne (“to open”), matching English “I open” or “I am opening.” The infinitive åpne is used after modal verbs (e.g. skal åpne, må åpne), but here you’re simply stating what you do/are doing now, so you use the present form åpner.