A percentage, a proportion (especially per hundred).

“only a small percent attain the top ranks”

One part per hundred; one percent.

A part of a larger whole, usually in such a form that it is able to be separated from other parts.

“I’d like another piece of pie.”

A single item belonging to a class of similar items

“a piece of machinery”

One of the figures used in playing chess, specifically a higher-value figure as distinguished from a pawn; by extension, a similar counter etc. in other games.

A rectangular piece of thick paper or thin cardboard intended to be written on and mailed without an envelope. In the case of a picture postcard one side carries a picture or photograph.