A rotor.
Q: Why is a helicopter called a "Chopper"? A: I think the names comes from the sound of the blades make: whop-whop or chop-chop. FYI, the helicopters that have the loud popping of the blades are usually a 2-blade of the Bell Helicopter design. The multi-blade helicopters do not have a sound as distinctive as the Bell helicopters. The sound comes from the blade striking the vortex generated by the blade ahead of it.
A rapidly revolving item is called a "spinning" object. Examples include a spinning top, carousel, or rotating blade.
rotor
The main lifting blades make up the rotor
The rotor blade is the airfoil on helicopters.
Yes, many small helicopters have 3 blades
The rotor blades when spinning creates what is called the rotor disk, the disk is tilted in the direction that the pilot wishes to go.
A group of helicopters.
I think you're talking about Peahats.
It is the major part of the rotor. Helicopters can have 3 up to 8 blades on a rotor.
it is called heliphololigy
Robert B. Taylor has written: 'Helicopter rotor blade design for minimum vibration' -- subject(s): Rotors (Helicopters), Stability of helicopters