「頭のいい人」? 「頭がいい人」?
 

I really don't understand when to use の and when to use が

I always connect nouns and adjectives using が

For example:

髪が長いです。

But when I use 頭がいい人, my teacher says it should be 頭のいい人.

Is it because there is another noun 人 after the adjective いい?


Which of the following is correct?

髪が長い人? 髪の長い人?

No. That's not the reason.

Strictly speaking, 頭がいい人 isn't really incorrect but native speakers prefer saying 頭のいい人 because the sound の is easier on the Japanese ear than that of が.

Again, both are correct but the native speakers' choice will be the latter.

Thank you again Nagoya.

But what if there is nothing after the adjective.

For example, 彼女の顔が綺麗です.　

Do native speakers say 彼女の顔の綺麗です.

彼女の顔が綺麗です > 彼女の顔は綺麗です

Your sentence with が can only be used in limited situations. Suppose you and I are looking at a pic of 5 girls. I ask you, "Which ones do you find pretty?" and you can say by pointing to one of the girls, "彼女の顔が綺麗です".

No. We never say 彼女の顔の綺麗です. This sentence lacks the subject marker, which is は.

の can sub in for が in phrases that modify a noun. That's basically the rule. It doesn't sub in anywhere else.

For example,
頭がいい人はおもしろい。ー＞頭のいい人はおもしろい 。
鈴木さんは頭がいい。ー／ー＞鈴木さんは頭のいい。 wrong wrong wrong