Their are many different ways of descibing waterwheels, which are often contradictory and potentially confusing. For clarity rather than using traditional names, those defined by the Cooperative Patents Classification (CPC), a joint enterprise between the American and European Patent Offices, shall be used.
Overshot - any wheel that where the water enters above the axle .
Undershot - any wheel where the water enters below the axle.
Potential Energy (PE) or Gravity Wheel - any wheel where the majority of energy harnessed is PE.
PE Dynamic Wheel - any wheel were PE is converted to KE before entering the wheel.
Kinetic Energy (KE) or Impulse Wheel - any wheel where the majority of energy harnessed is KE.
Bucket Wheel - any wheel where water is caught in a bucket.
Blade - any wheel where an apron or wheel pit is used in conjunction with a blade.
The above terms allow all types of wheel to be described.