En postkasse står bak huset.

Norwegian has two grammatical genders in the written standard (Bokmål): common (n-words) and neuter (t-words). The indefinite article en is used with common-gender nouns, while et is used with neuter nouns.

• postkasse is a common-gender noun ⇒ en postkasse
• hus is neuter ⇒ et hus

Definiteness in Norwegian is marked on the noun itself with a suffix:

• Neuter nouns like hus add -et for the definite singular: hus → huset (“the house”).
• Common-gender nouns add -en for the definite singular: stol → stolen (“the chair”).

In this sentence, postkasse is being introduced for the first time (so it’s indefinite – en postkasse), whereas huset is assumed known or contextually given, so it appears in the definite form (huset).

bak is a preposition meaning “behind.” In Norwegian you place it directly before the noun (in its correct form):

• indefinite: bak et hus (“behind a house”)
• definite: bak huset (“behind the house”)

There is no extra article or case ending beyond the normal definite suffix -et on huset.

In Norwegian, position verbs agree with the object’s posture:

• stå (“to stand”) for upright objects
• ligge (“to lie”) for objects resting flat or horizontal

A mailbox is typically upright, so you say står bak huset. If you talked about a fallen plank, you’d use ligger: ei grein ligger på bakken (“a branch lies on the ground”).

Yes. Norwegian main clauses follow the V2 rule: the finite verb must be the second element. If you start with an adverbial phrase (Bak huset), you invert subject and verb:

1. Adverbial first: Bak huset
2. Verb second: står
3. Subject third: en postkasse
   → Bak huset står en postkasse.

Norwegian tends to form compound nouns by merging words into one:

• post (mail) + kasse (box) → postkasse
  This is standard in both Bokmål and Nynorsk.