Øyeblikket var avgjørende.

Øyeblikket is the definite form of øyeblikk.

• et øyeblikk = a moment
• øyeblikket = the moment

In this sentence, Norwegian is talking about a specific moment, so it uses the definite form directly on the noun.

This is very common in Norwegian. Instead of a separate word like the, Norwegian usually adds the definiteness to the end of the noun:

• en bil = a car

• bilen = the car

• et hus = a house
• huset = the house

So:

• et øyeblikk = a moment
• øyeblikket = the moment

Because Norwegian usually expresses the by adding an ending to the noun.

Here, -et is the definite ending for a neuter singular noun:

• øyeblikk is a neuter noun
• so øyeblikket means the moment

English uses a separate article:

• the moment

Norwegian usually uses a suffix:

• øyeblikket

This is one of the biggest differences between English and Norwegian grammar.

Var is the past tense of å være = to be.

So:

• er = is / am / are
• var = was / were

That means:

• Øyeblikket er avgjørende = The moment is crucial
• Øyeblikket var avgjørende = The moment was crucial

In your sentence, the speaker is talking about something in the past, so var is correct.

Avgjørende means something like:

• decisive
• crucial
• critical
• determining

In this sentence, it is an adjective describing øyeblikket.

So the structure is:

• Øyeblikket = the subject
• var = the verb
• avgjørende = an adjective after to be

This is similar to English:

• The moment was decisive

Because avgjørende is one of those adjectives that usually keeps the same form.

It comes from a form ending in -ende, and adjectives of this type are generally not changed for gender or number in normal use:

• et avgjørende øyeblikk = a decisive moment
• øyeblikket var avgjørende = the moment was decisive
• avgjørende øyeblikk = decisive moments

So even though øyeblikket is a neuter singular noun, the adjective stays avgjørende.

This is different from adjectives like stor:

• en stor bil
• et stort hus
• husene er store

But with avgjørende, the form stays the same.

Because this is a sentence with to be.

When an adjective comes after å være and describes the subject, it is called a predicative adjective:

• Øyeblikket var avgjørende
• Bilen er stor
• Huset er gammelt

This is the same basic idea as in English:

• The moment was crucial
• The car is big
• The house is old

If the adjective came before the noun, it would be an attributive adjective instead:

• et avgjørende øyeblikk = a crucial moment

So:

• et avgjørende øyeblikk = adjective before the noun
• øyeblikket var avgjørende = adjective after was

A native English speaker often finds ø difficult, because English does not really have the same vowel.

A rough guide:

• øye sounds a bit like the first part of bird in some accents, but with rounded lips
• blikket has a short i, like bit

Very roughly, you can think of it as something like:

• UH-yuh-blik-ket

But that is only approximate.

A few useful pronunciation notes:

• ø is a rounded front vowel; you make a sound somewhat like e in her, but round your lips
• y in Norwegian is also rounded, unlike English y
• the double kk means the preceding vowel is short

If you want a safer beginner goal, try to clearly separate it into parts:

• øye
  • blikk
    • et

Not always, but it often overlaps with moment or instant.

Øyeblikk can mean:

• a very short time: just a moment
• a significant point in time: a crucial moment
• a brief instant

Examples:

• Vent et øyeblikk. = Wait a moment.
• Det var et vakkert øyeblikk. = It was a beautiful moment.
• Øyeblikket var avgjørende. = The moment was decisive.

So in your sentence, it is not just any tiny instant in a literal sense; it refers to an important point in time.

Yes, but that means something slightly different.

• Øyeblikket var avgjørende = The moment was decisive
• Det øyeblikket var avgjørende = That moment was decisive

Adding det points more clearly to a particular moment, often one already mentioned or strongly identified in context.

So both are possible, but:

• without det, it is simply the moment
• with det, it is more like that moment

No, this is very standard Norwegian word order.

The sentence follows a simple pattern:

• Subject
  • Verb
    • Complement

So:

• Øyeblikket = subject
• var = verb
• avgjørende = complement

This is exactly the kind of straightforward sentence learners see early on.

If you changed the order, it would usually only happen for special reasons, such as in a subordinate clause or with fronting:

• Jeg husker at øyeblikket var avgjørende. = I remember that the moment was decisive.

But as a main clause, Øyeblikket var avgjørende is the normal order.

This sentence is standard Bokmål.

It would also be perfectly understandable to Norwegian speakers generally, because the words are common. The exact form here looks like the kind of sentence a learner would usually meet in Bokmål.

Key forms showing standard Bokmål usage include:

• var
• øyeblikket
• avgjørende

So if you are studying mainstream written Norwegian, you can treat this as a normal Bokmål sentence.