Learn Hardcore Norwegian: Hun glemmer lunsjboksen hjemme.

The infinitive is glemme (to forget). glemmer is the present tense (presens) form, so it describes a current or habitual action: “she forgets.”

Why is lunsjboksen written as one word, and what does the -en ending indicate?

Norwegian often forms compound nouns by joining two words. Here lunsj (lunch) + boks (box) = lunsjboks (lunchbox). The -en ending is the definite singular marker, so lunsjboksen means “the lunchbox.”

What is the difference between hjem and hjemme, and why is hjemme used here?

hjem is used when indicating movement toward home (“go home”), while hjemme is an adverb meaning “at home” (location). Since the sentence describes where she forgets it, you use hjemme to mean “at home.”

Why does hjemme appear at the end of the sentence, rather than immediately after the verb?

The typical word order for a Norwegian main clause is Subject – Verb – Object – Adverbial. Adverbials of place (like hjemme) usually come after the object. Hence: Hun (S) glemmer (V) lunsjboksen (O) hjemme (Adv).

Could you replace hjemme with a prepositional phrase like på skolen? How would that affect the sentence?

Yes. You can substitute another place adverbial:
Hun glemmer lunsjboksen på skolen.
This means she leaves her lunchbox at school instead of at home. The structure remains S – V – O – Adv.

Can you use the past tense of glemmer here, and how would the sentence change?

Yes. The past tense of glemme is glemte. So you’d say:
Hun glemte lunsjboksen hjemme.
That shifts the action into the past: “She forgot the lunchbox at home.”