Weight (symbolized w ) is a quantity representing the force exerted on a particle or object by an acceleration field, particularly the gravitational field of the Earth at the surface. In the International System of Units ( SI ), weight can be expressed in terms of the force, in newton s, exerted on a mass in a gravitational field. In the English system, the standard unit of weight is the pound (lb), which is the force produced by gravitational acceleration on approximately 0.454 kg of mass at the Earth's surface.
Weight is not the same thing as mass. Mass is a literal representation of the amount of matter in a particle or object, and is independent of external factors such as speed, acceleration, or applied force (as long as relativistic effects are small enough to be neglected). Weight has meaning only when an object having a specific mass is placed in an acceleration field. At the Earth's surface, a kilogram mass weighs about 2.2 pounds, for example. But on Mars, the same kilogram mass would weigh only about 0.8 pounds, and on Jupiter it would weigh roughly 5.5 pounds.