adhesion and cohesion, attractive forces between material bodies. A distinction is usually made between an adhesive force, which acts to hold two separate bodies together (or to stick one body to another) and a cohesive force, which acts to hold together the like or unlike atoms, ions, or molecules of a single body. However, both forces result from the same basic properties of matter. A number of phenomena can be explained in terms of adhesion and cohesion. For example, surface tension in liquids results from cohesion, and capillarity results from a combination of adhesion and cohesion. The hardness of a diamond is due to the strong cohesive forces between the carbon atoms of which it is made. Friction between two solid bodies depends in part upon adhesion.