kono hon wa takai desu.

topic particle

Breakdown of kono hon wa takai desu.

• です: to be
• 本ほん: book
• 高たかい: expensive
• この: this

Questions & Answers about kono hon wa takai desu.

What does この mean, and why can’t we just use これ before 本?

この is a demonstrative adjective meaning “this,” and it must be followed by a noun.

• この本 literally “this book.”
  By contrast, これ is a pronoun meaning “this (thing),” so it stands alone (e.g. これは本です “This is a book.”).

Why is 本 followed by は instead of another particle like を?

In この本は高いです, は marks the topic of the sentence (“as for this book…”).

• を would mark a direct object for an action verb, but here we’re describing a state with an adjective, so there’s no object—only a topic.

Why is は pronounced “wa” here, not “ha”?

The hiragana は normally reads “ha,” but when it functions as the topic marker particle, its pronunciation changes to “wa.”
This is a special rule for particles and doesn’t affect は when it’s part of a native word.

What kind of word is 高い, and why does it end with です?

高い is an i-adjective meaning “expensive” (or “tall,” depending on context).

• In casual speech you could simply say この本は高い.
• Adding です makes it polite: この本は高いです “This book is expensive (polite).”

Do all adjectives in Japanese need です after them?

No.

• i-adjectives like 高い can stand alone in casual speech.
• na-adjectives (e.g. 静か “quiet”) require です or another copula when used predicatively: この部屋は静かです.
  Using です simply raises the politeness level.

Why is there no word for “is” like in English (“This book is expensive”)?

Japanese typically uses です or the copula だ to express “to be.” In polite speech, です serves both as “is/am/are” and a politeness marker.
So 高いです covers “is expensive” without a separate verb.

Why aren’t we mentioning “it” or “this book” as the subject?

Japanese often omits subjects or objects when they’re clear from context.
In この本は高いです, この本 is already the topic, so you don’t need an extra “it.” You wouldn’t say “それはこの本は高いです.”

How would I turn this into a question (“Is this book expensive?”)?

Simply add the question particle か at the end:

• この本は高いですか。
  You can also rise your intonation in casual speech without か:
• この本は高い？