Pounds (lb) are units of weight or mass commonly used in the United States customary and British imperial systems of measurement. The pound has the same definition in both systems.

1. United States Customary System: In the United States customary system, the pound is used as the primary unit of weight. It is defined as 16 ounces, or 0.45359237 kilograms. This is often referred to as the avoirdupois pound. The pound is widely used in everyday life for measuring the weight of people, objects, and commodities.
2. British Imperial System: In the British imperial system, the pound is also used as the primary unit of weight. It is defined the same way as in the U.S. customary system, with 1 pound equal to 16 ounces or approximately 0.45359237 kilograms. The pound is commonly used in the United Kingdom and other countries that follow the British imperial system.

Pounds are used to measure a wide range of objects and substances, including body weight, groceries, packages, and industrial materials. They are commonly encountered in contexts such as commerce, engineering, construction, and everyday life.