Pound force (lbf) is a unit of force in the Imperial system, commonly used in the United States. It measures the force exerted by gravity on a mass of one pound at the Earth's surface. This means that a pound force is equivalent to the weight of one pound under standard gravity, which is approximately 32.2 feet per second squared. In scientific contexts, pound force is often used in engineering and physics to describe forces acting on objects. It is important to distinguish pound force from pound mass (lbm), as the two represent different concepts; pound mass measures the amount of matter, while pound force measures the effect of gravity on that matter.