Dette er den fjerde boken.

This is the fourth book.

Breakdown of Dette er den fjerde boken.

• være: to be
• boken: the book
• dette: this
• den: the

Questions & Answers about Dette er den fjerde boken.

Why does the sentence start with dette and not denne?

Because dette is being used as a stand-alone demonstrative pronoun: this / this thing.

In Norwegian:

• dette = this when it stands on its own
• denne = this when it directly goes with a common-gender noun

So:

• Dette er den fjerde boken. = This is the fourth book.
• Denne boken er den fjerde. = This book is the fourth.

A useful shortcut:

• dette = this by itself
• denne + noun = this + noun

Why is it den fjerde boken and not just fjerde boken?

Because Norwegian normally uses den/det/de before a definite noun phrase when there is an adjective or ordinal in front of the noun.

Here, fjerde (fourth) comes before boken, so Norwegian needs:

• den fjerde boken

Compare:

• boken = the book
• den fjerde boken = the fourth book

So the extra den is required because the noun is definite and it has a modifier before it.

Why do we have both den and -en in boken? Doesn't that mean the twice?