<P> A solid bounded by a cylindrical surface and two parallel planes is called a ( solid ) cylinder . The line segments determined by an element of the cylindrical surface between the two parallel planes is called an element of the cylinder . All the elements of a cylinder have equal lengths . The region bounded by the cylindrical surface in either of the parallel planes is called a base of the cylinder . The two bases of a cylinder are congruent figures . If the elements of the cylinder are perpendicular to the planes containing the bases , the cylinder is a right cylinder , otherwise it is called an oblique cylinder . If the bases are disks ( regions whose boundary is a circle ) the cylinder is called a circular cylinder . In some elementary treatments , a cylinder always means a circular cylinder . </P>
how many plane surfaces does a cylinder have
two