Glossary
What is a rotorcraft?
The category of aircraft that get their lift from rotating blades rather than fixed wings. It covers helicopters and gyroplanes both, so it is a wider word than either: every gyroplane is a rotorcraft, and so is every helicopter, but a rotorcraft is not necessarily a gyroplane.
That is the whole entry for now. The longer version, with the mechanics and worked examples, is still to be written. See autorotation for how those read once they exist.