Personopplysningene er private.

It is a compound noun, which is very common in Norwegian.

You can break it down like this:

• person = person
• opplysning = piece of information, detail
• -ene = the, plural

So personopplysningene means the personal details / the personal data.

Norwegian often writes compounds as one word, where English would usually use two or more words.

In Norwegian, the definite article is often attached to the end of the noun instead of standing in front of it.

So:

• opplysninger = information/details, plural
• opplysningene = the information/details

That same pattern applies to the full compound:

• personopplysninger = personal data
• personopplysningene = the personal data

The ending -ene marks definite plural for this noun.

Here is the full pattern:

• en opplysning = a piece of information
• opplysningen = the piece of information
• opplysninger = pieces of information / data
• opplysningene = the pieces of information / the data

Because opplysning is the main noun in the compound, the whole word follows that same pattern:

• personopplysning
• personopplysninger
• personopplysningene

Er is the present tense of å være, which means to be.

So:

• er = am / is / are

In this sentence, it links the subject to the adjective:

• Personopplysningene er private = The personal data are private

This works just like English are in a sentence such as The documents are private.

Because the subject is plural.

The adjective privat changes form depending on what it describes:

• privat = singular
• private = plural

So:

• Dokumentet er privat = The document is private
• Dokumentene er private = The documents are private

Since personopplysningene is plural, the correct form is private.

It is plural.

A good clue is the ending -ene, which here marks definite plural.

Even though English often uses data or information in ways that do not always feel clearly plural, Norwegian is treating this as a plural noun here: the personal details / the data.

Yes. That would also be correct, but the meaning changes slightly.

• Personopplysninger er private = Personal data are private, in general
• Personopplysningene er private = The personal data are private, referring to specific data

So the version with -ene is definite and usually points to data already known from the context.

No. This is a very normal Norwegian sentence pattern:

• Subject
  • verb
    • adjective/complement

So:

• Personopplysningene = subject
• er = verb
• private = adjective

It works much like English:

• The personal data are private

Usually it is very close, but the exact English translation depends on context.

It can mean things like:

• personal information
• personal data
• personal details

In legal, administrative, or privacy-related contexts, personal data is often the best match.

In Norwegian compounds, the last part is usually the main noun. That part determines things like gender and inflection.

Here, the last part is opplysning. That is why the forms are based on opplysning:

• opplysning
• opplysninger
• opplysningene

The first part, person-, just narrows the meaning.

So literally, it is something like person-information, but in natural English we say personal information or personal data.