Measuring instantaneous rates is the most direct way of determining the rate law of a reaction, but it is not always convenient, and it may not be possible to do so with precision.
piece (pÄs) n. 1. A thing considered as a unit or an element of a larger thing, quantity, or class; a portion: a piece of string. 2. A portion or part that has been separated from a whole: a piece of pie. 3. An object that is one member of a group or class: a piece of furniture.
1 an amount or portion forming a separate mass or structure; bit. a piece of wood. 2 a small part, item, or amount forming part of a whole, esp. when broken off or separated. a piece of bread. 3 a length by which a commodity is sold, esp. cloth, wallpaper, etc.