Et dusin er tolv.

Because dusin is a neuter noun in Norwegian Bokmål.

Norwegian indefinite articles agree with the noun’s gender:

• en for common gender
• et for neuter

So you say:

• en bil = a car
• et hus = a house
• et dusin = a dozen

That is why et is correct here.

Yes. Dusin corresponds closely to English dozen.

It is used for a group of twelve items, especially in everyday expressions such as:

• et dusin egg = a dozen eggs
• et dusin roser = a dozen roses

So its use is very similar to English.

Er means is / are / am, depending on context.

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

Examples:

• Han er her. = He is here.
• Vi er klare. = We are ready.
• Et dusin er tolv. = A dozen is twelve.

Because Norwegian number words normally do not change form here.

Tolv simply means twelve, and it stays the same whether it is used on its own or after a verb like er.

Examples:

• Det er tolv. = It is twelve.
• Hun har tolv bøker. = She has twelve books.
• Et dusin er tolv. = A dozen is twelve.

So there is no special ending needed.

Yes, it is very similar.

The structure is:

• Et dusin = subject
• er = verb
• tolv = complement

So the pattern is basically:

subject + verb + complement

That matches English A dozen is twelve very closely.

Yes, in some contexts it can.

In et dusin, et is the indefinite article, so it works like English a.

But Norwegian et/ett can also be related to the number one. This is why learners sometimes notice a connection.

A simple way to remember it:

• before a neuter noun, use et as the article: et hus, et dusin
• the standalone neuter form of one is often ett

So in this sentence, think of et as a, not as a stressed one.

A rough learner-friendly pronunciation is:

et du-SEEN er tolv

A few notes:

• dusin has stress on the second syllable: du-SIN
• the u sound in Norwegian is not exactly like English oo; it is more rounded and more forward in the mouth
• er is usually short and light in everyday speech
• tolv sounds somewhat like tolv, with a clear v at the end

Exact pronunciation varies by dialect, but that approximation will help you get started.

Yes. It is perfectly natural as a simple factual statement, especially in a learning context.

In real everyday speech, people might more often use dusin inside a phrase, such as:

• Jeg kjøpte et dusin egg. = I bought a dozen eggs.

But Et dusin er tolv is completely normal if you are defining the word or explaining what it means.

Yes. Both are possible:

• Et dusin er tolv.
• Et dusin er 12.

Writing tolv is more common in teaching materials and full sentences, while 12 is also perfectly understandable and natural in many contexts.