The pound (lb.) is a non-metric unit of weight, or mass, that equals 16 ounces and 0.453 kg. The abbreviation “lb.” comes from the Roman word “libra.” One-twelfth of the libra, the Roman uncia, is the ancestor of the English ounce.

The pound is widely used in the United States customary, the International System of Units (SI), and the imperial systems of measurement. After the introduction of a metric system, the pound unit of mass became irrelevant in many countries.