Definition 1 of 2
Plain English Meaning
The spinning part of a machine. In helicopters it's the big set of blades on top. In an engine it's the shaft and wheels that spin inside. In a magneto or generator it's the spinning magnet that produces electrical current.
Full Definition
The rotating assembly of an aircraft, engine, or machine that produces lift, thrust, compression, or electrical output through its motion. In a helicopter, the rotor is the system of rotating blades that generates lift and directional control. In a turbine engine, it is the spinning shaft assembly carrying the compressor and turbine wheels. In a magneto or generator, it is the rotating magnetic component that induces current in the surrounding stationary windings.
Context Anchor
Seen in helicopter preflight, rotor-system discussions, and descriptions of rotating parts inside electrical or ignition equipment.
Derivation
From the Latin 'rotare,' meaning 'to turn' or 'to rotate.' Anything called a rotor is, by definition, the part that spins -- as opposed to the stator, which stays still.
Why Pilots Care
Proper rotor function is essential for all helicopter flight; damage or mismanagement can cause loss of control.
Analogy
Like a giant overhead fan that pushes air down hard enough to lift the whole machine.
Intuition Check
Do not assume rotor only means helicopter blades. In aviation, a rotor can also be the spinning part inside a machine such as an alternator or magneto.
Example Sentence 1
Before lifting off, the pilot brought the main rotor up to operating RPM and checked the engine and rotor needles were joined.
Example Sentence 2
As rotor speed increased, the helicopter began to lift off the ground.