Definition
A movable control surface hinged to the trailing edge (rear edge) of each wing, near the wingtip, used to roll the airplane around its longitudinal axis. The ailerons move in opposite directions: when one goes up, the other goes down. This produces unequal lift between the two wings, which banks the airplane left or right.
Plain English
The flaps near each wingtip that the pilot uses to tilt the airplane left or right. Pushing the control wheel or stick to the left makes the left wing drop; pushing right makes the right wing drop.
Context Anchor
Seen during the visual preflight assessment when checking that each aileron is attached, moves freely, and responds correctly to the control wheel or stick.
Derivation
From the French aileron, meaning 'little wing' (a diminutive of aile, 'wing'). The name fits well — an aileron is, quite literally, a small wing-like surface attached to the main wing.
Why Pilots Care
Ailerons provide the primary means of lateral control; they are required for all turns, banks, and corrections for roll.
Intuition Check
An aileron is not the same as a flap. Ailerons tilt the airplane left or right; flaps mainly help the wing produce more lift at lower speeds.
Example Sentence 1
During the preflight walkaround, the pilot checked that each aileron moved freely up and down and was secure at its hinges.
Example Sentence 2
The pilot applied left aileron to begin a coordinated bank into the turn.