Abrasive Wear – Also referred to as “cutting wear.” This occurs when hard surface asperities or hard particles have embedded themselves into a soft surface. Adhesion – The force or forces causing two materials, such as a lubricating grease and a metal, to stick together. Base – A refined mineral oil, free of additives, used as a component in a lubricant blend. Bleeding – The separation of oil from a grease structure. A certain amount of bleeding is considered desirable in greases, since this tends to provide continuous oil lubrication to bearings. Emulsion – A liquid in which another immiscible liquid is suspended. Water and oil can be emulsified under certain conditions of oil type and severe agitation. Emulsifying agents are sometimes added to oils for production of cutting fluids, which are to be mixed with water. Fiber – In lubricating grease, the form in which soap thickeners occur, the soaps crystallizing in threads, which are of the order of 20 or more times as long as they are thick. Friction – A resistance to motion between two surfaces in contact. Influent – The fluid entering a component. Injector – A positive displacement (oil or grease) lubricant measuring valve that dispenses lubricant when main line pressure rises and resets when its compressed return spring forces the measuring piston back to its rest position. Lubricant – Any substance used to separate two surfaces in motion and reduce the friction or wear of the surfaces. Miscible – Liquids capable of forming a liquid solution or uniform mixture between themselves, e.g. gasoline and oil are miscible. NLGI Grade Number – Numbers assigned by the NLGI to classify greases according to their hardness as measured by a cone penetration test. Monitor – An electrical or electronic device that compares (monitors) a lubrication systems operation to a user selected time frame, or delivery rate. Oil – A general term for a water-insoluble thick liquid that possesses lubricating properties. Petroleum – Term applicable to crude oil and the hydrocarbon products and materials that are derived from it. Pumpability – The ability of a lubricating grease to flow under pressure through the line, nozzle and fitting of a grease dispensing system at varying temperatures. Syneresis – Loss of liquid lubricant from a lubricating grease due to shrinkage or rearrangement of the structure. Viscosity – The measurement of a fluid’s resistance to flow. It is defined as the shear stress on a fluid element divided by the rate of shear; “high viscosity” applies to a fluid which does not flow easily, “low viscosity” to a fluid, such as water, which flows easily.