Systemnøkkelen og nøkkelkopien har samme nøkkelnummer.

Because both nouns are in the definite singular form.

In Norwegian, many masculine and common-gender nouns take -en when they mean the ...:

• en nøkkel = a key
• nøkkelen = the key

The same pattern applies inside compounds:

• systemnøkkel = system key

• systemnøkkelen = the system key

• nøkkelkopi = key copy
• nøkkelkopien = the key copy

So the sentence is talking about specific items: the system key and the key copy.

Yes. Norwegian uses compound nouns very freely, just like German, and often more than English does.

Here is how they break down:

• systemnøkkel = system
  • nøkkel
• nøkkelkopi = nøkkel
  • kopi
• nøkkelnummer = nøkkel
  • nummer

A useful rule: the last part of the compound is the main noun, and it decides the grammatical gender and basic meaning.

For example:

• nøkkelkopi is a kind of kopi (copy)
• nøkkelnummer is a kind of nummer (number)

This is why compounds are so common in Norwegian: instead of using many separate words, Norwegian often packs the idea into one noun.

Because Norwegian uses ha (to have) for this kind of idea: possessing or sharing a feature.

So:

• har samme nøkkelnummer = have the same key number

This is the normal way to say it in Norwegian. English also often says have the same number, so the structure is quite similar.

Using er would sound wrong here, because the key and the copy are not being identified as the number itself. They simply have that number.

Samme is the normal form meaning same, and it does not change for gender or number in the way many other adjectives do.

Examples:

• samme nøkkel = the same key
• samme nummer = the same number
• samme hus = the same house
• samme biler = the same cars

So in your sentence:

• samme nøkkelnummer = the same key number

This is one of the easier words for learners, because you do not have to memorize several agreement forms.

Because samme often works without an article in Norwegian in expressions like this.

So Norwegian naturally says:

• ha samme navn = have the same name
• ha samme adresse = have the same address
• ha samme nummer = have the same number

That is why:

• har samme nøkkelnummer sounds natural

English usually needs the in the same, but Norwegian often does not use an article in this pattern.

The structure is:

Subject + verb + object/complement

More specifically:

• Systemnøkkelen og nøkkelkopien = the subject
• har = the verb
• samme nøkkelnummer = what they have

So the sentence follows normal Norwegian main-clause word order.

It is also a good example of verb-second word order in a simple sentence. Since the subject comes first, the finite verb comes right after it:

• Systemnøkkelen og nøkkelkopien
  • har
    • ...

If something else came first, the verb would still stay in second position.

Because two singular nouns joined by og (and) make a plural subject in meaning.

So:

• Systemnøkkelen = singular
• nøkkelkopien = singular
• Systemnøkkelen og nøkkelkopien = together, plural

That is why the sentence means that both items share the same key number.

In the present tense, Norwegian verbs do not change for singular vs. plural, so you still get har either way. But semantically, the subject is plural.

Sometimes yes, but the meaning and style are slightly different.

• nøkkelkopien = the key copy / the copy key, a compact compound noun
• kopien av nøkkelen = the copy of the key, a more expanded phrase

Norwegian often prefers compound nouns where English might use of or a noun phrase.

So nøkkelkopien sounds very natural and efficient here. It may also sound a bit more like a technical or practical label, which fits a sentence about keys and key numbers.

You could make it indefinite like this:

• En systemnøkkel og en nøkkelkopi har samme nøkkelnummer.

That would mean something like A system key and a key copy have the same key number.

Compare:

• Systemnøkkelen og nøkkelkopien ... = the system key and the key copy ...
• En systemnøkkel og en nøkkelkopi ... = a system key and a key copy ...

So the original sentence refers to specific, known items.

In Norwegian compounds, the main stress usually falls on the first part of the compound.

So roughly:

• SYSTEMnøkkelen
• NØKKELkopien
• NØKKELnummer

That first element tends to carry the strongest stress, even though the word may be long.

Also, the letter ø is important in all three words with nøkkel. It is not the same sound as o. English speakers often need practice with that vowel.

So if you want to sound natural, focus on:

• clear ø
• strong stress on the beginning of the compound

It sounds natural, but also somewhat practical or technical, which makes sense because it is about keys and identification numbers.

Words like:

• systemnøkkel
• nøkkelkopi
• nøkkelnummer

are exactly the kind of vocabulary you might see in instructions, locksmith contexts, building management, or security systems.

So the sentence is grammatically normal and natural, but the vocabulary belongs to a specific real-world context rather than everyday casual conversation.