目に見えないものの「こ・そ・あ・ど」はむずかしいですね。
(1) こ
is almost the same as "this" or "such" and easier to understand than そ and あ.
It is used what the speaker is going to show to the listener or what the listener is going to see/hear soon (or sometimes something they are seeing/hearing).
e.g.
あなたはこんな話を聞いたことがありますか？
Have you ever heard of a story like this?
Have you ever heard of such a story?
(Then the story follows...)
これが私の夢です。
This is my dream.
(After a speech on something, for instance.)
Both そ and あ can be translated as "that" but the meaning is different.
(2) あ
Somthing that the speaker has in mind.
The listener need to ask what the speaker refers.
e.g.
あんなことが起こるなんて予想してなかった。
I did not expect something like that could happen.
(Then the listener feel like to ask what "that" incident is.)
ああいう人になりたいな。
I want to be someone like that.
(3) そ
Something specific, the very thing, that particular, etc.
Both the speaker and listener shares it, and both of them know what is being referred.
Maybe it is closer to the pronoun "it" than "that".
e.g.
その話はもう何度も聞いたよ。
I've already heard of that story several times.
そんなこと言うなよ！
Don't say such a thing!
こ・そ・あ・ど
Two friends are talking about films.
亜紀子「ねえ、あの映画もう観た？」
健「あの映画って、どの映画？」
亜紀子「ほら、恵子たちが先週観に行ったっていう映画」
健「ああ、あの映画かあ。それなら、観たよ」
亜紀子「面白かった？」
健「感動したよ。」
亜紀子「へえ、あなたが？珍しいわね。感動だなんて」
健「やっぱりクリント・イーストウッドは最高だね」
亜紀子「ええ？いったい何の映画の話をしてるの？」
健「『父親たちの星条旗』じゃないの？」
亜紀子「それは今週見た映画でしょ。私が言ってるのは『プラダを着た悪魔』よ」
健「ごめん、ごめん。その映画はまだ観てないんだ」
