润滑(lubrication)
在滑动面间介入种种物质，以减少磨耗和摩擦力。润滑剂可间接地控制腐蚀、调节气温、用作电绝缘体、去除污染物或制止振动等。史前人类则用泥和芦苇来润滑橇、木材或岩石。而当第一部载重马车以动物脂肪润滑轮轴後，动物脂肪即广被采用，直到19世纪原油成为润滑剂的主要来源。原油一直是一些产品的基础，这些产品为符合汽车、飞机、柴油机车、涡轮喷射发动机和各种动力机械等的特殊润滑需要而设计出来。润滑可分为流体膜润滑、界面润滑及固体润滑三种基本型︰流体膜润滑（系用流体膜完全隔开滑动面）；界面润滑（其表面间的摩擦取决於表面与润滑剂的性质，而非润滑剂的黏度）；固体润滑（用於流体润滑剂无法对负载产生足够的阻力或抵挡极高的温度时）。主要的润滑剂有流体、油状润滑剂（以石油为主或合成物，包括兽脂）；固体润滑剂（如石墨、钼、二硫化物、软金属、腊和塑胶；以及气体润滑剂。
English version：
lubrication
Introduction of any of various substances between sliding surfaces to reduce wear and friction. Lubricants may secondarily control corrosion, regulate temperature, electrically insulate, remove contaminants, or damp shock. Prehistoric peoples used mud and reeds to lubricate sledges, timbers, or rocks. Animal fat lubricated the axles of the first wagons and continued in wide use until crude oil became the chief source of lubricants. Crude oil has been the basis of products designed for the specific lubricating needs of automobiles, aircraft, locomotives, turbojets, and all other power machinery. There are three basic varieties of lubrication: fluid-film (in which a fluid film completely separates sliding surfaces), boundary (in which the friction between surfaces is determined by the properties of the surfaces and properties of the lubricant other than viscosity), and solid (used when liquid lubricants lack adequate resistance to load or temperature extremes). The principal lubricants are liquid, oily materials (petroleum-based or synthetic, and including greases); solids (such as graphite, molybdenum disulfide, soft metals, waxes, and plastics); and gases.
