Nattillegget er lavt.

It is a compound noun:

• natt = night
• tillegg = supplement / extra payment / addition

So nattillegg usually means a night supplement, often an extra amount of pay for working at night.

The form nattillegget means the night supplement.

In Norwegian, the definite article is usually added to the end of the noun.

So:

• et nattillegg = a night supplement
• nattillegget = the night supplement

This is very common in Norwegian. English uses a separate word (the), but Norwegian often uses a suffix instead.

Because the compound is based on natt + tillegg.

When these are combined, the t from natt and the t at the start of tillegg come together, giving nattillegg. Then the definite ending -et is added:

• natt
  • tillegg → nattillegg
• nattillegg
  • -et → nattillegget

So the spelling reflects how the compound is built.

Because tillegg is a neuter noun: et tillegg.

In Norwegian, adjectives often agree with the noun. With a singular neuter noun, many adjectives take -t when used like this:

• en bil er lav = a car is low
• et tillegg er lavt = a supplement is low

So in Nattillegget er lavt, the adjective is neuter singular to match nattillegget.

Here it is an adjective, not an adverb.

It describes the noun nattillegget:

• Nattillegget = the subject
• er = is
• lavt = low

This is called a predicative adjective: it comes after er but still describes the noun.

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

So:

• å være = to be
• er = is / am / are

In this sentence, er means is.

The word order is:

Subject + verb + adjective

• Nattillegget = subject
• er = verb
• lavt = adjective

So it works very much like English The night supplement is low.

This is also consistent with normal Norwegian main-clause word order, where the finite verb comes in the second position.

Sometimes, but it would not mean exactly the same thing.

• lavt = low, often used about levels, rates, amounts, pay, prices, and figures
• lite = small / little, often focusing more on size or quantity

With pay or extra compensation, lavt is usually the more natural choice if you mean the amount is low.

So Nattillegget er lavt sounds very natural for The night supplement is low.

The indefinite singular form is et nattillegg.

The full set is:

• et nattillegg = a night supplement
• nattillegget = the night supplement
• nattillegg = night supplements
• nattilleggene = the night supplements

This is useful because the sentence uses the definite singular form.

Most often in work and pay contexts.

For example, it can refer to:

• extra pay for working night shifts
• a nighttime surcharge
• an additional amount paid because work happens at night

So if someone says Nattillegget er lavt, they are often talking about compensation and saying that the extra amount for night work is not very high.

In careful speech, the t is there, but in natural speech it may sound less strong than an English learner expects.

What matters most is remembering the spelling and the grammar:

• lav for some common forms
• lavt for singular neuter

So even if pronunciation varies a bit in connected speech, you should still learn lavt as the correct written form here.