Lungene trenger luft.

Because lungene is the definite plural form: the lungs.

Norwegian very often uses the definite form when talking about body parts, even in general statements. So Lungene trenger luft sounds natural in the same way English says The lungs need air.

If you said lunger, that would mean lungs in an indefinite sense, but it would sound less natural here.

The full pattern is:

• en lunge = a lung
• lungen = the lung
• lunger = lungs
• lungene = the lungs

So in your sentence, lungene is the plural definite form.

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

Some useful forms are:

• å trenge = to need
• trenger = need / needs / am needing
• trengte = needed
• har trengt = have/has needed

In this sentence, trenger means need.

No.

• trenger = need
• må = must / have to

So:

• Lungene trenger luft = The lungs need air
• Lungene må ha luft = The lungs must have air

These are close in meaning, but not identical. Trenger expresses a need; må expresses necessity or obligation.

Because luft is usually treated as an uncountable noun, like English air.

In general statements, Norwegian often uses the noun without an article:

• Lungene trenger luft
• Vi trenger vann
• Planter trenger lys

So luft here means air in general, not a particular air.

In Bokmål, luft is usually treated as masculine when it appears in a definite form, so you often see luften = the air.

In this sentence, though, you do not see the gender directly, because luft is being used as a bare uncountable noun.

You may also hear lufta in some dialects or less formal usage.

It literally means air.

If you specifically mean oxygen, Norwegian uses oksygen.

So this sentence is the ordinary everyday way to express the idea. It is not using the scientific word oksygen.

It follows the basic Norwegian statement pattern:

subject + verb + object

So here:

• Lungene = subject
• trenger = verb
• luft = object

That is the normal word order for a simple statement.

In simple statements like this, yes. But Norwegian also follows the verb-second rule, which means the finite verb stays in the second position.

For example:

• Lungene trenger luft
• For å fungere trenger lungene luft

In the second sentence, For å fungere comes first, so trenger still stays in second position.

The ng is pronounced like the ng in English sing.

So you should not pronounce it as a separate n plus a hard g sound.

That means:

• lungene has the ng sound
• trenger also has the ng sound

Also, the ending -er is often pronounced fairly weakly in many varieties of Norwegian.

Yes, you could say Lungene behøver luft, and it would be understood.

But trenger is usually the more common, everyday choice. Behøver can sound a bit more formal or less conversational, depending on context.

So for a basic sentence like this, trenger is the most natural option.