Bølgehøyden er høy.

Because Norwegian usually writes compound nouns as a single word.

Here, the parts are:

• bølge = wave
• høyde = height

So bølgehøyde is literally wave-height, written as one word, not two.

This is very common in Norwegian. English often uses separate words where Norwegian uses a compound.

The dictionary form is bølgehøyde.

The sentence uses the definite singular form:

• bølgehøyde = wave height
• bølgehøyden = the wave height

You may also see the noun listed as ei bølgehøyde or en bølgehøyde, depending on how the feminine noun is treated in Bokmål.

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

So:

• høyde = height
• høyden = the height

The same thing happens in compounds:

• bølgehøyde = wave height
• bølgehøyden = the wave height

So English uses a separate word, the, but Norwegian often adds the definiteness directly to the noun.

Because the adjective has to match the noun in gender and number.

After er, the adjective is a predicative adjective, and its form depends on what the subject is:

• høy = masculine/feminine singular
• høyt = neuter singular
• høye = plural

So here:

• bølgehøyden is singular
• it is not neuter

Therefore høy is the correct form.

Compare:

• Bilen er høy. = The car is tall/high.
• Huset er høyt. = The house is tall/high.
• Bølgene er høye. = The waves are high.

No, this is the normal word order for a simple statement:

• Subject + verb + complement
• Bølgehøyden er høy

A yes/no question would change the order:

• Er bølgehøyden høy? = Is the wave height high?

More generally, Norwegian main clauses follow the verb-second pattern. In this sentence, the subject comes first, so the verb naturally comes second.

A rough guide:

• høy sounds somewhat like hoy, but with a Norwegian vowel sound, not a regular English o
• ø is the tricky letter: it is somewhat like the vowel in British English bird, but with rounded lips

So:

• bølge ≈ BURL-guh / BØL-guh (very approximate)
• høy ≈ hoy, but with a more fronted rounded vowel
• bølgehøyden has the stress mainly at the start: BØL-ge-høy-den

If you know IPA, høy is approximately /hœʏ/.

It is grammatical and understandable, and it can sound natural in a technical or weather-related context.

That said, some learners notice that it feels a bit repetitive because høyde and høy are closely related, a bit like saying the height is high.

In real usage, people might also say things like:

• Bølgene er høye. = The waves are high.
• Det er høy bølgehøyde. = There is a high wave height.
• Bølgehøyden er tre meter. = The wave height is three meters.

So the sentence is fine, especially as a learning example, but other phrasings are also common.

Yes, possibly.

Høyde is a feminine noun, so a feminine definite form bølgehøyda can occur in Bokmål, especially depending on dialect and writing style.

But bølgehøyden is also correct and very common, especially in formal or technical Bokmål.

So as a learner, it is useful to recognize both:

• bølgehøyden
• bølgehøyda

Both can mean the wave height.

It breaks down like this:

• bølge = wave
• høyde = height
• -n / -en = the definite ending

So structurally, it is:

bølge + høyde + definite ending

That makes it a very typical Norwegian compound noun with definiteness added at the end. This pattern is extremely common in Norwegian, so it is worth getting used to.