Høreapparatbatteriet er nytt.

Because Norwegian very often makes compound nouns by joining words together.

Here:

• høreapparat = hearing aid
• batteri = battery

So:

• høreapparatbatteri = hearing-aid battery
• høreapparatbatteriet = the hearing-aid battery

This is much more natural in Norwegian than writing the words separately.

-et is the definite singular ending for many neuter nouns.

The base noun is:

• et batteri = a battery

The definite form is:

• batteriet = the battery

In the compound, the last part controls the grammar, so:

• et høreapparatbatteri = a hearing-aid battery
• høreapparatbatteriet = the hearing-aid battery

Because batteri is a neuter noun.

The adjective ny changes to match the noun:

• ny for common gender singular
• nytt for neuter singular
• nye for plural and some other cases

Since høreapparatbatteriet is singular and neuter, you say:

• Høreapparatbatteriet er nytt.

This is a very common question.

After a verb like er, the adjective is a predicative adjective. Predicative adjectives in Norwegian usually agree with gender and number, but not with definiteness.

So:

• et batteri → Batteriet er nytt.
• en bil → Bilen er ny.
• husene → Husene er nye.

But when the adjective comes before the noun, definiteness matters:

• et nytt batteri = a new battery
• det nye batteriet = the new battery

So:

• Høreapparatbatteriet er nytt is correct
• not Høreapparatbatteriet er nye

Because Norwegian often puts the at the end of the noun instead of using a separate word.

Compare:

• et batteri = a battery
• batteriet = the battery

So in høreapparatbatteriet, the idea of the is already built into the word.

The basic form is:

• et høreapparatbatteri = a hearing-aid battery

That tells you two important things:

1. the noun is neuter because it takes et
2. the definite singular form will usually be -et:
   • høreapparatbatteriet

No, this is a very standard Norwegian sentence pattern:

• [subject] + [verb] + [adjective]

So:

• Høreapparatbatteriet = subject
• er = is
• nytt = new

It works just like:

• Bilen er ny. = The car is new.
• Huset er stort. = The house is big.

A rough breakdown is:

• hø-re-ap-pa-rat-bat-te-ri-et

A few tips:

• ø has no exact English equivalent; it is similar to the vowel in French deux or German schön
• the stress is usually strongest in the main parts of the compound, especially apparat and batteri
• the final -et is usually pronounced lightly

You do not need to pronounce every part with equal stress; compounds usually flow together naturally.

Yes, you could.

That means:

• Batteriet til høreapparatet er nytt.
• literally: The battery of the hearing aid is new.

This is understandable and correct, but høreapparatbatteriet is more compact and often more natural if you mean the specific type of battery belonging to a hearing aid.

So both are possible, but the compound noun is very typical Norwegian.

Yes.

It is made from:

• høre = hear / hearing
• apparat = device, apparatus

So:

• høreapparat = hearing aid

Then Norwegian adds another noun:

• høreapparat + batteri = hearing-aid battery

This shows how common compounds are in Norwegian: you can build longer nouns by stacking words together.