15. A quadrilateral having both pairs of opposite sides parallel to each other Parallelogram
16. Circle A closed plane curve consisting of all points at a given distance from the center
17. a surface or solid bounded by two parallel planes and generated by a straight line moving parallel to the given planes and tracing a curve bounded by the planes and lying in a plane perpendicular or oblique to the given planes Cylinder
18. a solid geometric figure generated by the revolution of a semicircle about its diameter; a round body whose surface is at all points equidistant from the center Sphere
19. Semicircle half of a circle; the arc from one end of a diameter to the other
20. Intersecting lines Two lines in the same plane are not parallel and intersect at a certain point