The resistance opposed by a body to the separation of its particles. This property depends on the force of cohesion, or on that which chemists call affinity, joined to the arrangement of the particles to their figure, and other circumstances. The differences between hard bodies, such as are, soft, and such as are elastic, have been thus defined. The soft body yields to pressure without spontaneously returning to its previous form on taking off the pressure; the elastic body returns to its original form upon removing the force applied; while that which is strictly hard breaks asunder when overcome by the force brought against it. It is, however, justly doubted whether there is any body in nature that is perfectly hard, perfectly soft, or perfectly elastic; for all bodies seem to possess these three qualities, though in proportions indefinitely various.