Katalognummeret står på plateomslaget.

Because Norwegian usually marks definiteness by adding an ending to the noun instead of using a separate word.

• et katalognummer = a catalog number
• katalognummeret = the catalog number
• et plateomslag = a record cover / sleeve
• plateomslaget = the record cover / sleeve

So both katalognummeret and plateomslaget already include the meaning of the.

Norwegian normally writes compound nouns as one word.

• katalognummer = catalog + number
• plateomslag = record + cover/sleeve

This is very common in Norwegian. English often writes similar expressions as two words, but Norwegian usually joins them into one. The last part of the compound is the main part, so nummer is the head in katalognummer, and omslag is the head in plateomslag.

The basic indefinite forms are:

• et katalognummer
• et plateomslag

Both are neuter nouns, which is why the indefinite article is et and the definite ending is -et.

So:

• et katalognummer → katalognummeret
• et plateomslag → plateomslaget

This is a very common Norwegian pattern. The verb stå literally means stand, but Norwegian often uses verbs of position where English would simply use be.

In a sentence like this, står means something like:

• is written
• is printed
• appears

So Katalognummeret står på plateomslaget is not saying the catalog number is physically standing. It means that the catalog number is written or printed on the cover.

This is very natural in Norwegian.

Here på means on.

It is used because the catalog number is written on the surface of the cover. Norwegian often uses på for text or markings on a surface:

• på etiketten = on the label
• på siden = on the page
• på skjermen = on the screen

So på plateomslaget is the natural choice.

No. In this context, plate means a record, disc, or sometimes more generally a music release, depending on context.

So plateomslag means the record cover, album cover, or sleeve, not the cover of a kitchen plate.

This is one of those words where context matters a lot.

The sentence has normal main-clause word order:

• Katalognummeret = subject
• står = verb
• på plateomslaget = prepositional phrase

So the structure is basically:

subject + verb + place

Norwegian is a V2 language, which means the finite verb usually comes second in main clauses. That becomes especially important if you move another part to the front.

For example, you can also say:

På plateomslaget står katalognummeret.

That is still correct, because står remains in second position.

Yes. Because of Norwegian V2 word order, the verb must still stay in second position.

So you say:

På plateomslaget står katalognummeret.

Not:

På plateomslaget katalognummeret står.

This is a very common difference from English, and it is something learners need to get used to early on.

It is singular definite: the catalog number.

If you wanted the plural, you would use:

• katalognumre = catalog numbers
• katalognumrene = the catalog numbers

So:

• Katalognummeret = the catalog number
• Katalognumrene = the catalog numbers

A fully indefinite version would be:

Et katalognummer står på et plateomslag.

Grammatically, that is fine, but it sounds more general and less natural in many contexts. The original sentence with definite forms sounds more like you are talking about a specific catalog number and a specific cover, or making a general statement about where that number is found in a known context.

So the original definite sentence is often the most natural one.