Gjenbruk er viktig.

Because gjenbruk is being used as a general, abstract noun here. Norwegian often leaves out the article when talking about something in general.

So Gjenbruk er viktig works like English Recycling is important or Reuse is important, not The recycling is important.

If you were talking about a specific case, you would usually make that clearer in some other way, for example with a definite form or extra context.

It is a noun.

More specifically, it is an abstract noun meaning reuse or, depending on context, sometimes recycling in a broad environmental sense.

It is related to the verb å gjenbruke, which means to reuse.

For example:

• Gjenbruk er viktig. = the noun
• Det er viktig å gjenbruke. = the verb

Not always.

Gjenbruk more literally means reuse: using something again instead of throwing it away.

Resirkulering is more specifically recycling: processing material so it can become something new.

So the difference is often:

• gjenbruk = reuse
• resirkulering = recycling

But in environmental slogans or simple teaching sentences, gjenbruk may sometimes be translated more loosely if the larger topic is recycling.

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

So this sentence uses a very basic pattern:

• subject + er + adjective

Here that gives:

• Gjenbruk = subject
• er = is
• viktig = important

So grammatically, it is a very straightforward sentence.

This is the normal word order for a simple Norwegian main clause.

Norwegian usually follows the verb-second rule in main clauses, often called V2. That means the finite verb usually comes in the second position.

Here:

1. Gjenbruk
2. er
3. viktig

Because the subject comes first, the verb comes right after it.

Because viktig is a predicate adjective. It comes after er and describes the subject.

This is the same basic idea as in English:

• Recycling is important
• Gjenbruk er viktig

So viktig is not placed before gjenbruk here, because it is not directly modifying the noun inside a noun phrase. It is completing the statement after er.

Not visibly in this sentence.

The adjective is viktig, and that same form is used here. Even though Norwegian adjectives often change depending on gender and number, viktig is one of those adjectives where the singular forms look the same.

For example:

• en viktig ting
• et viktig spørsmål

But in the plural, you usually get:

• viktige

Example:

• Disse tingene er viktige.

So in Gjenbruk er viktig, there is no visible change to the adjective.

A rough English-friendly pronunciation would be:

YEN-brook er VIK-tih

A few helpful points:

• gj at the start of gjenbruk is usually pronounced roughly like y in yes
• gjen sounds roughly like yen
• bruk sounds somewhat like brook, though the Norwegian vowel is not exactly the same as English
• viktig is often pronounced roughly VIK-tih, and the final g is often weak or not clearly pronounced in everyday speech

This is only an approximation, but it is a good starting point.

Yes, absolutely.

Both are natural, but they feel slightly different:

• Gjenbruk er viktig = direct and simple
• Det er viktig med gjenbruk = a little more like It is important to have/use reuse/recycling

The first version is especially common in short statements, slogans, and simple explanations.

Yes. That is also very natural.

The difference is:

• Gjenbruk er viktig focuses on the concept or practice
• Det er viktig å gjenbruke focuses on the action of reusing

Both are correct, and both would sound natural in everyday Norwegian.

It works in both Bokmål and Nynorsk.

Nothing in Gjenbruk er viktig clearly marks it as only one written standard. So if you saw this sentence by itself, it would fit both.