Definition
In a piston aircraft engine, a ring is a flexible metal band fitted into a groove around the outside of a piston. Each piston typically carries several rings stacked in separate grooves: compression rings near the top to seal combustion gases above the piston, and an oil control ring lower down to scrape excess oil off the cylinder wall and return it to the crankcase.
Plain English
A small metal band that wraps around the piston and presses against the cylinder wall. It seals the burning fuel-air mixture above the piston and keeps engine oil from getting where it shouldn't.
Context Anchor
Seen in engine heat management discussions, especially when reading about piston engines, cylinder condition, oil control, compression, and overheating.
Derivation
Ring comes from an old word meaning a circular band. That fits the engine meaning directly: the part is shaped like a circle and sits around the piston like a band.
Why Pilots Care
Worn or stuck rings allow heat to build up inside the piston, leading to power loss, detonation, or engine damage.
Intuition Check
Do not read ring here as just any circle or loop. In this engine context, it means a specific metal sealing band around a piston.
Example Sentence 1
High oil consumption between oil changes can be a sign of worn piston rings.
Example Sentence 2
Proper ring seating after an overhaul lets the engine transfer piston heat efficiently to the cooling fins.