Plain English Meaning
The drag or rubbing force that slows things down when two surfaces slide against each other. It also produces heat, which is why machines get hot and parts wear out over time.
Full Definition
The resistance to motion that occurs when two surfaces are in contact and one moves, or tries to move, relative to the other. In aviation maintenance, friction generates heat and wear, which is why moving parts are lubricated, fitted with bearings, or designed with low-friction materials.
Context Anchor
Seen in aircraft maintenance when discussing moving parts, brakes, tires, bearings, controls, and lubrication.
Derivation
From the Latin fricare, meaning 'to rub.' The original sense — rubbing — is exactly what friction does at a , which makes the technical meaning easy to onto.