Friction, lubrication, wear and corrosion

Tribology is defined as the science that deals with the interaction between surfaces in motion and consequences of that interaction, i.e. friction, lubrication and wear. Sir William Hunter described the tribological features of synovial joints succinctly in 1743: 'Both are covered with a smooth crust, to prevent natural abrasion; connected with strong ligaments to prevent dislocation; and enclosed in a bag that contains a proper fluid deposited there, for lubricating the two contiguous surfaces.'