Pound is a unit of weight used primarily in the United States. In science and technology, weight refers to the gravitational force on an object, and the pound is used as a unit of force. This unit also appears in the term pounds per square inch (psi), which is used as a measure of pressure. In commercial and everyday use, the term weight is understood to mean mass (quantity of matter), and so the pound is also used as a unit of mass.
In the system of weights called the avoirdupois << av uhr duh POYZ >> system, which is used to weigh most objects, there are 16 ounces to a pound. As a unit of force, the avoirdupois pound is equivalent to 4.448 newtons in the metric system; as a unit of mass, 0.454 kilogram in the metric system. In the troy weight system, used throughout the world to measure precious metals, a pound equals 12 ounces and is equivalent to 0.373 kilogram.
The abbreviation for pound is lb. The abbreviation stands for the Latin word libra, which means pound or balance. Libra was the name of a unit of weight used by the ancient Romans, and it was the name for a balance, or scale, that Romans used to measure weight. The symbol # is sometimes used for pound.
