A piece is a distinct item, that you can pick up and carry around, for example.
A unit is a conceptual piece, but may not be possible or convenient to deal with as an actual piece. For example, flooring material may be sold in units of square yards (or square meters), but may only come in rolls that are several yards (or meters) wide.
A unit is a conceptual piece, but may not be possible or convenient to deal with as an actual piece. For example, flooring material may be sold in units of square yards (or square meters), but may only come in rolls that are several yards (or meters) wide.
