Vi trenger elleve billetter.

In Norwegian, verbs do not change according to the subject the way they do in English.

So you get:

• jeg trenger = I need
• du trenger = you need
• vi trenger = we need
• de trenger = they need

The form trenger stays the same. That is much simpler than English.

Trenger is the present tense of the verb å trenge, which means to need.

So:

• å trenge = to need
• trenger = need / am needing / are needing, depending on context

In this sentence, it simply means need.

This is the normal Norwegian main-clause word order:

subject + verb + object

So:

• Vi = subject
• trenger = verb
• elleve billetter = object

This is very similar to English: We need eleven tickets.

Because trenger is a finite verb, not an infinitive.

In English, to need is the basic dictionary form.
In Norwegian, the dictionary form is å trenge.

But in a normal sentence, you usually use the conjugated form:

• å trenge = to need
• vi trenger = we need

So the å disappears because the verb is being used as the main verb of the sentence.

Because numbers above one normally take a plural noun in Norwegian.

So:

• en billett = one ticket
• to billetter = two tickets
• elleve billetter = eleven tickets

That is why billetter is plural here.

Norwegian usually does not use an article in front of an indefinite plural noun.

Compare:

• en billett = a ticket
• billetter = tickets

So:

• Vi trenger en billett = We need a ticket
• Vi trenger elleve billetter = We need eleven tickets

This is similar to English, where you also say eleven tickets, not eleven the tickets or eleven some tickets.

The singular noun is billett.
The plural indefinite form is billetter.

A useful pattern is:

• en billett = a ticket
• billetten = the ticket
• billetter = tickets
• billettene = the tickets

So the ending -er is a very common plural ending in Norwegian.

Billetter means tickets in a general or indefinite sense.
Billettene means the tickets, so it is definite.

Compare:

• Vi trenger elleve billetter = We need eleven tickets
• Vi trenger de elleve billettene = We need the eleven tickets

In your sentence, the indefinite form billetter is correct because it just means eleven tickets, not the eleven tickets.

Yes, in many contexts you can write 11.

So both of these can appear:

• Vi trenger elleve billetter.
• Vi trenger 11 billetter.

Writing out the number is often preferred in learning materials and in more careful writing, while digits are very common in everyday use.

It can do both, depending on context.

Vi trenger elleve billetter can mean:

• we need them now
• we will need them for some plan or event

Norwegian often uses the present tense for something current or near-future when the context makes it clear.

Yes. Another common verb is å behøve.

So you may also see:

• Vi trenger elleve billetter
• Vi behøver elleve billetter

Both can mean We need eleven tickets, but trenge is very common and natural in everyday speech.

A rough English-style guide is:

vee TREN-ger EL-leh-veh bee-LET-er

A few helpful notes:

• vi sounds like vee
• trenger has a short e sound
• elleve has three syllables
• billetter has the stress on the -lett- part

The exact Norwegian sounds are a bit different from English, but that approximation is a good start.

Not always. Norwegian follows the V2 rule in main clauses, which means the verb usually comes in the second position.

So:

• Vi trenger elleve billetter.
• I morgen trenger vi elleve billetter.

Notice that when I morgen comes first, the verb trenger comes next, before vi.

That is a very important Norwegian word-order rule.