Cylinders (solids)

GGeometric solid figure having two ends comprising equal and parallel circles, and the intervening curved surface is such as would be traced out by a straight line moving parallel to itself with its ends in the circumferences of these circles. If the direction of this straight line is perpendicular to the planes of the circles, the figure is a right cylinder; if not, an oblique cylinder. In modern geometry, the term is used for the solid generated by a straight line moving always parallel to itself and describing any fixed curve, not necessarily a circle. Used in common language to refer to hollow forms as well as solid.