Hi, this is Yuyujin.

Here I would like to review “A= B“ expression.
And I would like to introduce the negative form of “A=B” expression.

A Wa B Desu
(Aは B です。)

AGa B Desu
(Aが Bです。)

Here Ais a noun and a subject.
B is A‘s name, character or situation.

Let’s get started.

“A Wa BDesu(AはB です。)” “AGa B Desu(AがB です。)”

“A Ga(Aが)” describes “the only A is B.” and “the things except A are not B“.
“A Wa(Aは)” describes just “the A is B.” and the things except A are not mentioned in this sentence.

For example

Toukyou Ga Nihon No Shuto Desu
( とうきょうがにほんのしゅとです。)
Tokyo is a Japanese capital.

This sentence would like to describe
“Not Osaka, Not Nagoya, Tokyo is a Japanese capital.”

We also can say

Toukyou Ha Nihon No Shuto Desu
(とうきょうはにほんのしゅとです。)
Tokyo is a Japanese capital.

We can make the question form of this.

“A Wa B Desu Ka(AはB ですか。)” “A Ga B Desu Ka(AがB ですか。)”

Toukyou Ga Nihon No Shuto Desu Ka
(とうきょうがにほんのしゅとですか。)
Is Tokyo a Japanese capital?

Toukyou Ha Nihon No Shuto Desu Ka
(とうきょうがにほんのしゅとですか。)
Is Tokyo a Japanese capital?

The answer is like below.

Toukyou Ga Nihon No Shuto Desu Ka
(とうきょうがにほんのしゅとですか。)
Is Tokyo a Japanese capital?

“A Wa B Dewaarimasen (AはBではありあせん。)”