I have answered your question already.
Where?
I would sooner believe mathematicians.
Lee Kleir, PhD Electrical Engineering and Computer Science & Girls, The University of Texas at Austin (1976)
Originally Answered: In number how many sides does a cylinder have?
"A cylinder has 1 side which wraps around circular areas in the two ends. If the ends are enclosed then there are 2 circular sides for a total of 3 sides, two of which are flat circles and one curved side."
or....
"If it's a solid cylinder then it has three - a circular face at each end and a single surface that goes all the way round the middle which can be 'opened up' as a rectangle
If the cylinder is hollow (technically a tube) then it has two faces - an inner one and an outer one."