Circumference: is a curved closed line in which all points are at the same distance from fixed point called centre of the circumference. Cylinder: have two congruent, parallel bases like prism, but instead of polygons, those bases are circles. The altitude of a cylinder is any perpendicular segment from the plane of one base to the plane of the other. Cone: has a circle as a base; its radius is the radius of the circle. The vertex of a cone is the greatest perpendicular distance from any base. The altitude of a cylinder is the perpendicular segment from the vertex to the plane of the base. Sphere: is the set of all points in space from given point. The given distance is caled radius, and given points is the centre of the sphere. A hemisphere is half a sphere and its circular base. Reflection: is a transformation in which every point of a figure appears an equal distance on the other side of a given line. That line called line reflection.