Vi er tolv personer.

• Vi = we
• er = are
• tolv = twelve
• personer = people / persons

So the sentence is literally We are twelve persons, which in natural English is usually There are twelve of us or We are twelve people.

Norwegian often expresses this idea with we are + number when talking about how many people are in a group that includes the speaker.

So:

• Vi er tolv personer = There are twelve of us
• literally: We are twelve people

English often prefers There are twelve of us, but Norwegian is perfectly natural with Vi er ...

Because Norwegian uses to be for this kind of statement, just like English in We are twelve people.

• er is the present tense of å være = to be
• har means have, and that would not fit here

So:

• Vi er tolv personer = correct
• Vi har tolv personer would usually mean something more like We have twelve people, for example in an organization or team, not There are twelve of us

Yes, absolutely.

Vi er tolv is very natural and often enough if the context already makes it clear that you are talking about people.

• Vi er tolv = There are twelve of us / We are twelve
• Vi er tolv personer is a little more explicit

In everyday speech, omitting personer is often more common.

Both can refer to people, but they are used a bit differently.

• personer is the straightforward plural of person
• folk can mean people in a more collective sense

So you may hear:

• Vi er tolv personer
• Vi er tolv folk

But personer is often the safer and more standard choice for learners, especially in careful or neutral language.

No. Tolv does not change.

Norwegian numbers like tolv are normally the same regardless of the noun:

• tolv personer
• tolv biler
• tolv hus

Unlike some other words in Norwegian, the number itself stays the same.

Because the sentence refers to more than one person.

• singular: en person = one person
• plural: personer = people / persons

Since tolv is more than one, the noun must be plural:

• tolv personer

Not exactly in tone or frequency.

In English, persons sounds formal in many situations, and people is much more common.

In Norwegian, personer is normal and natural. It does not sound unusually formal in the way English persons often does.

So although personer is related to persons, you should usually think of it as matching ordinary English people in many contexts.

The word order is:

subject + verb + number + noun

• Vi = subject
• er = verb
• tolv personer = complement

This is very normal Norwegian main-clause word order.

You switch the verb and subject:

• Er vi tolv personer?

That means:

• Are we twelve people?
• or Are there twelve of us?

This verb-before-subject pattern is common in Norwegian yes/no questions.

You change er to var:

• Vi var tolv personer = We were twelve people / There were twelve of us

So:

• present: Vi er tolv personer
• past: Vi var tolv personer

A simple learner-friendly approximation is:

vee ehr tvoll pehr-SOO-ner

A few notes:

• Vi sounds like vee
• er is often pronounced lightly in everyday speech
• tolv has a short vowel and a clear lv ending
• personer has stress on the second syllable: per-SO-ner

Pronunciation varies a bit by dialect, but this is a useful starting point.

Yes, it is natural and correct.

That said, in everyday speech many speakers would often simply say:

• Vi er tolv

because personer is easy to understand from context.

So both are good:

• Vi er tolv personer = explicit
• Vi er tolv = shorter and very common