Han bruker et falskt navn.

Because navn is a neuter noun in Norwegian. Neuter nouns take et in the indefinite singular.

• et navn = a name
• compare:
  • en bil = a car
  • et hus = a house

So you have to learn navn as et navn.

This is because adjectives must agree with the noun they describe.

Since navn is a neuter singular noun, the adjective takes -t:

• en falsk adresse
• et falskt navn

So the pattern is:

• en + adjective + common-gender noun
• et + adjective + neuter noun

That is why it is et falskt navn, not et falsk navn.

Here, bruker means uses.

It is the present tense of å bruke = to use.

Examples:

• Jeg bruker telefonen. = I use the phone.
• Han bruker et falskt navn. = He uses a false name.

A useful thing to remember is that Norwegian present tense verbs often end in -r:

• å bruke → bruker
• å snakke → snakker
• å bo → bor

This is the normal word order for a statement in Norwegian:

subject + verb + rest of sentence

So:

• Han = subject
• bruker = verb
• et falskt navn = object

This is very similar to English:

• He uses a false name.

If you turned it into a yes/no question, the order would change:

• Bruker han et falskt navn? = Does he use a false name?

Normally, no. In this sentence, navn is a countable singular noun, so you usually need an article.

Natural:

• Han bruker et falskt navn.

Unnatural or incomplete in most contexts:

• Han bruker falskt navn.

English sometimes also requires the article here:

• He uses a false name not usually
• He uses false name

So Norwegian works similarly in this case.

Not exactly, but they can overlap.

• et falskt navn literally means a false/fake name
• et alias means an alias

In many situations, they can refer to the same idea, but falskt navn emphasizes that the name is not the person’s real one.

So:

• Han bruker et falskt navn strongly suggests he is presenting himself under a name that is not real or not his own.

Here, navn is singular.

The whole phrase means a false name, so it is one name.

A tricky thing is that navn has the same form in singular and plural indefinite:

• et navn = a name
• navn = names

Definite forms:

• navnet = the name
• navnene = the names

So in your sentence, the article et tells you clearly that it is singular.

That would be:

det falske navnet

Why?

• navnet = the name
• in the definite form, the adjective usually takes -e
• and you also often add the determiner det with a neuter noun

So:

• et falskt navn = a false name
• det falske navnet = the false name

This is a very common pattern in Norwegian.

A careful approximation is:

han BROO-ker et FALSKT nav(n)

A few notes:

• bruker has a rounded vowel that does not exist exactly in English
• et is often pronounced very lightly in normal speech
• falskt can be tricky because of the consonant cluster at the end
• navn may sound like the final consonants are compressed together

If you say it slowly and clearly, that is perfectly fine as a learner: Han / bruker / et / falskt / navn

In ordinary grammar, yes: han means he.

So:

• Han bruker et falskt navn. = He uses a false name.

In older or more literary Norwegian, han can sometimes refer to certain masculine nouns, but that is not what is happening here. In this sentence, it simply means he.