English Grammar: Confusion between IN and ON?

Question

I'm really confused when to use in and on

For example,

The sad look on/in her face.

The sadness in/on her eyes.

She slapped him on/in the face.

She kicked him on/in the nuts.

There's a dirt on/in his face.

Please help!!! Please give rules/tips in identifying when to use IN and ON properly.

Thanks~

Answer 1

Favorite Answer

The sad look on her face. // the look could actually be IN or ON, I'd say OF or IN

The sadness in her eyes. // we look IN others' eyes

She slapped him in the face. // it's typical to assault others IN rather than ON, unless it's the butt xD

He kicked him in the nuts. // same as the previous

There's dirt on his face. // the dirt is laying on the surface of his face, not in his face. That would mean that the dirt would in his skin.

There aren't any rules. Actually, it's just a thing that everybody says and speakers of English get used to and begin to say themselves.

Answer 2

The sad look on her face.

The sadness in her eyes.

She slapped him on the face. although "across the face" would be better

She kicked him in the nuts.

There's dirt on his face. no "a", or you could say "a piece of dirt"

It's usually "on a face" because your face is like a surface, "in eyes" because the eyes are kind of "inside" your head (I guess, I haven't heard a rule about that). And you kick "in" and punch "in" but slap "across"--maybe because kicking and punching go deeper and slapping goes wider? I'm not sure.