Det dype hullet er farlig.

Because hull is a neuter noun in Norwegian.

• a hole = et hull
• the hole = hullet

For definite noun phrases with a neuter noun, you use det:

• det dype hullet = the deep hole

If the noun were a common-gender noun (an en noun), you would normally use den instead.

Hullet is the definite singular form of hull.

The pattern is:

• et hull = a hole
• hullet = the hole

Many neuter nouns form the definite singular with -et.

So in this sentence, hullet means the hole, not just hole.

Yes, in a way they both contribute to definiteness. This is a very common Norwegian pattern called double definiteness.

When a definite noun has an adjective before it, Norwegian usually uses:

• a definite article/determiner + adjective + noun in definite form

So:

• det dype hullet = literally something like the deep hole
• not just dype hullet
• and not just det dype hull

This is normal Norwegian structure.

Compare:

• hullet = the hole
• det dype hullet = the deep hole

Because the adjective is placed before a definite noun, and in that position Norwegian usually uses the weak form of the adjective, which often ends in -e.

So:

• et dypt hull = a deep hole
• det dype hullet = the deep hole

Here is the contrast:

• dypt is used with an indefinite neuter singular noun
• dype is used in a definite phrase

So the change is not just about the noun being neuter; it is also about the whole phrase being definite.

The indefinite version is:

Et dypt hull er farlig.

That means A deep hole is dangerous.

Compare:

• Et dypt hull = a deep hole
• Det dype hullet = the deep hole

So the sentence changes from talking about any deep hole to talking about one specific deep hole.

Here farlig is a predicate adjective, meaning it comes after er and describes the subject.

In Norwegian, predicate adjectives often agree with the noun, but some adjectives do not add -t in the neuter singular. Farlig is one of them.

So:

• Hullet er farlig. = The hole is dangerous.

You can compare with another adjective that does change:

• Huset er stort. = The house is big.

But with farlig, the form stays farlig.

So in this sentence, farlig is simply the correct form.

Er is the present tense of å være (to be).

So:

• er = is / are

In this sentence:

• Det dype hullet er farlig.
• The deep hole is dangerous.

It links the subject (det dype hullet) with the description (farlig).

The subject is:

Det dype hullet

That whole phrase means the deep hole.

So the sentence breaks down like this:

• Det dype hullet = subject
• er = verb
• farlig = description/predicate adjective

In other words, the sentence says something about the deep hole.

Yes, but that means something different.

• Det dype hullet er farlig. = The deep hole is dangerous.
• Hullet er dypt. = The hole is deep.

In the first sentence, deep is part of the noun phrase: the deep hole.
In the second sentence, deep is what you are saying about the hole.

So:

• det dype hullet = adjective before the noun
• hullet er dypt = adjective after er

Both are correct, but they express different ideas.

This sentence uses very normal Norwegian main-clause word order:

• Subject + verb + complement

So:

• Det dype hullet
  • er
    • farlig

This is the same basic pattern as English:

• The deep hole
  • is
    • dangerous

Nothing unusual is happening with the order in this particular sentence.

A careful pronunciation is roughly:

deh DY-pe HULL-et er FAR-li

A few helpful notes:

• det is often pronounced more like de in natural speech
• dype has two syllables: DY-pe
• hullet has two syllables: HULL-et
• farlig is usually pronounced something like FAR-li

The exact pronunciation varies by dialect, but that rough version will help you get started.