Glossary
What is ground effect?
The drop in induced drag that occurs while an airplane is within roughly a wingspan of the surface, because the ground interferes with the wingtip vortices and the downwash behind the wing. It is why an airplane can feel as though it wants to float just above the runway, and why it can leave the ground before it has the speed to climb away.
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.