Thin means not having much fat or flesh. We use it to describe people or animals who are not fat. This is the simple, physical meaning.
My cat is very thin and small.
She is thin because she runs a lot.
Thin means not thick, having little width or depth. We say this about objects like paper, slices, or materials.
This book has thin pages.
She cut a thin slice of bread.
Thin can describe something that is weak or not rich, like soup or sound. It means there is not much substance or strength.
The soup tastes thin without salt.
She has a thin voice on the phone.
To thin means to make something less thick or less crowded. It can describe making things fewer or less strong by removing parts or mixing.
The forest thinned after the fire.
She thinned the paint with water.
Thin can describe a place or group with not many people or things close together. It means things are spread out or few.
The crowd was thin in the morning.
The trees here are thin and far apart.
Thin can be used to say something is weak or not good, like an excuse or reason. It means it is not strong or believable.
He gave a thin excuse for being late.
Her story sounds thin to me.
