gravity, also called gravitation, in mechanics, the universal force of attraction acting between all matter. ... On Earth all bodies have a weight, or downward force of gravity, proportional to their mass, which Earth's mass exerts on them. Gravity is measured by the acceleration that it gives to freely falling objects.In physics, gravitation is the force that pulls two masses toward each other. Believe it or not, every single particle of matter in the universe exerts gravitation on every other particle. The terms gravitation and gravity are often used interchangeably for the attraction between everything with energy or mass