Learn Hardcore Norwegian: Dersom heisen stopper, må personalet umiddelbart ringe sykehuset. - If the elevator stops, the staff must immediately call the hospital.

Dersom translates as if and is slightly more formal or common in written Norwegian. Hvis also means if, but is more frequent in everyday speech. You can generally use them interchangeably in conditional clauses.

Why is the noun heisen used instead of heis?

The base noun is heis (“elevator”). To make it definite singular, Norwegian adds a suffix. For masculine/feminine nouns like heis, you add -en, giving heisen (“the elevator”).

Why is stopper in the present tense, and why is present tense used here for a condition?

Stopper is the present tense of stoppe (“to stop”). In Norwegian (as in English), the present tense often expresses general or future conditions in “if”-clauses: “If the elevator stops …” = Dersom heisen stopper …. There’s no need for a separate future tense.

What is the role of må in this sentence?

Må is a modal verb meaning must or have to. It expresses obligation. Here it tells us that the staff is required to call the hospital immediately if the elevator stops.