Re: are the propellers of a windmill an example of a screw (a simple machine)?

I am not sure f you are correct or confused because I could not tell which 
side you were taking.  I checked the Encarta article you mentioned to see what might have confused you.  It is accurate.  A windmill or airplane or boat or sub, etc. propeller is an example of a screw.  The blades of the propeller correspond to the threads of smaller screws and are used to propel the screw through the air (or water) in the same fashion that wood screws pull themselves through wood.

B Self, Sherman, TX