Thinner

"thin plate of metal;  thin paper;  thin board;  thin covering"

"thin wire;  thin string"

"thin person"

"Water is thinner than honey."

"The trees of a forest are thin; the corn or grass is thin."

"Turpentine or mineral spirits can be used as a thinner for oil-based paints."

"A solid mane thinner is indispensable in finishing the looks of your horse."