Halsbåndet er nytt.

Because Norwegian often puts the definite article onto the end of the noun instead of using a separate word like the.

• et halsbånd = a collar
• halsbåndet = the collar

So -et here is the definite ending for a neuter noun.

Halsbånd is a neuter noun.

You can tell from its indefinite article:

• et halsbånd = a collar

In Norwegian, the main genders you will see in Bokmål are:

• en for masculine/common nouns
• ei for feminine nouns
• et for neuter nouns

Since the word is et halsbånd, it is neuter. That is also why the definite form is halsbåndet.

Because the adjective has to agree with the noun.

The adjective ny changes form depending on what kind of noun it describes:

• en ny bil = a new car
• et nytt halsbånd = a new collar
• nye biler = new cars

Here, the subject is halsbåndet, which is a singular neuter noun, so the adjective becomes nytt.

This same agreement also happens when the adjective comes after er:

• Halsbåndet er nytt.

Because in Norwegian, definiteness is usually built into the noun itself.

English uses a separate word:

• the collar

Norwegian usually uses an ending:

• halsbåndet

So halsbåndet already means the collar, and you do not need another word for the in this sentence.

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

So:

• å være = to be
• er = is / am / are, depending on context

Norwegian does not change the present-tense verb for different persons the way English does:

• jeg er = I am
• du er = you are
• han er = he is
• de er = they are

So in this sentence, er simply means is.

No, this sentence has very straightforward word order.

It follows the normal pattern:

• subject + verb + adjective

So:

• Halsbåndet = subject
• er = verb
• nytt = adjective

This is very similar to English:

• The collar is new.

Yes, and this is something learners often notice.

If the adjective comes before a definite noun, Norwegian usually uses:

• a definite determiner
• the adjective in its definite/plural form
• the noun in its definite form

For example:

• det nye halsbåndet = the new collar

Compare:

• et nytt halsbånd = a new collar
• halsbåndet er nytt = the collar is new
• det nye halsbåndet = the new collar

So nytt is used here because it is a predicate adjective after er, not because it is directly in front of the noun.

Yes. It is a compound noun made from:

• hals = neck
• bånd = band / strap

So halsbånd literally means something like neck-band, which is the Norwegian word for collar.

Compound nouns are extremely common in Norwegian, just as in German and unlike the more separate style often used in English.

The double t helps show that the vowel is short and that the final consonant is clearly pronounced.

For learners, the important point is:

• ny and nytt are different forms of the same adjective
• nytt is the neuter singular form

You do not need to think of the extra t as adding extra meaning by itself; it is simply part of the correct neuter form of ny.

Yes, but it would not mean exactly the same thing in the same context.

• Halsbåndet er nytt. = The collar is new.
• Det er nytt. = It is new or That is new, depending on context

So det can replace the noun if the listener already knows what you are talking about, but halsbåndet is more specific.