Oppgi serienummeret og referansenummeret.

Oppgi is the imperative form of the verb å oppgi.

That means the sentence is giving an instruction, like:

• Provide ...
• Enter ...
• State ...

In Norwegian, the imperative often looks like the verb stem without any subject. So instead of saying You provide the serial number..., Norwegian just says Oppgi ...

Also, the infinitive is å oppgi, while the imperative is just oppgi.

Because this is an imperative sentence.

In Norwegian, commands and instructions usually do not include the subject:

• Oppgi serienummeret. = Provide the serial number.
• Vent! = Wait!
• Kom inn. = Come in.

Just like English often leaves out you in commands, Norwegian does the same.

Because Norwegian very often forms compound nouns as one word.

So:

• serie
  • nummer → serienummer
• referanse
  • nummer → referansenummer

This is extremely common in Norwegian. Where English often writes noun combinations as separate words, Norwegian usually joins them:

• serial number → serienummer
• reference number → referansenummer

A good rule of thumb is: if English has a noun + noun combination, Norwegian often turns it into one compound word.

The ending -et is the definite article suffix for a singular neuter noun.

So:

• et serienummer = a serial number
• serienummeret = the serial number

And:

• et referansenummer = a reference number
• referansenummeret = the reference number

Unlike English, Norwegian usually puts the at the end of the noun as a suffix.

The key noun in both compounds is nummer, and nummer is a neuter noun:

• et nummer
• nummeret

In Norwegian compounds, the last part is the main noun, and it determines the gender. Since both words end in -nummer, both are also neuter:

• et serienummer
• serienummeret
• et referansenummer
• referansenummeret

So if you know the gender of the final element, that usually tells you the gender of the whole compound.

Because they are two separate definite nouns joined by og.

So Norwegian says:

• serienummeret og referansenummeret

not just:

• serienummer og referansenummeret

Each noun is being referred to specifically: the serial number and the reference number.

This is similar to English, where you would normally say the serial number and the reference number, not just serial number and the reference number, if both are definite.

Og simply means and.

It connects the two noun phrases:

• serienummeret
• referansenummeret

So the structure is:

• Oppgi
  • serienummeret
    • og
      • referansenummeret

Very straightforwardly: command + item 1 + and + item 2.

Yes. Oppgi is built from gi (to give) plus the prefix opp.

But you should learn å oppgi as its own verb, because its meaning is not just literally give up/up-give in this context. It commonly means:

• state
• provide
• enter
• give information

One important warning: å oppgi is not the same as å gi opp.

• å oppgi = to provide / state
• å gi opp = to give up

Same pieces, different order, different meaning.

Yes, it sounds like the kind of Norwegian you often see in:

• forms
• websites
• applications
• customer service messages
• official instructions

Oppgi ... is a very common instruction word in formal or semi-formal written Norwegian.

In everyday speech, someone might also say things like:

• Kan du oppgi serienummeret? = Can you provide the serial number?
• Skriv inn serienummeret. = Enter the serial number.

So the sentence is natural, but it has a clear instruction/form language feel.

The cluster can look strange to an English speaker. A simple learner-friendly approximation is:

• oppgi ≈ OPP-yee

A few helpful points:

• The pp shows that the preceding vowel is short.
• The g before i is not pronounced like a hard English g in go.
• For many learners, thinking of the second part as sounding a bit like yee is a useful approximation.

You do not need to pronounce each consonant separately in an exaggerated way. Just aim for a smooth two-part pronunciation.

Yes, but that would change the meaning.

Compare:

• Oppgi serienummeret og referansenummeret.
  = Provide the serial number and the reference number.

• Oppgi serienummer og referansenummer.
  = more like Provide serial number and reference number / Provide a serial number and a reference number

In instructions on forms, the definite form is very common because the form expects those specific pieces of information. So -et sounds natural here.