Altitude of a Cone  -  The segment with one endpoint at the vertex of a cone and the other in the plane that contains the base of the cone.

Altitude of a Pyramid  -  The segment with one endpoint at the vertex of a pyramid and the other at the center of the base of the pyramid.

Base of a Cone  -  The simple closed curve that bounds part of the cone.

Base of a Cylinder  -  One of two simple closed curves that lie in parallel planes.

Base of a Prism  -  One of two polygons that lie in parallel planes.

Base of a Pyramid  -  A polygon that bounds part of the pyramid.

Center of a Sphere  -  The fixed point in the interior of a sphere from which all points on the sphere are equidistant

Circular Cone  -  A cone whose base is a circle

Circular Cylinder  -  A cylinder whose base is a circle.

Concave Simple Closed Surface  -  A simple closed surface in which one or more segments* drawn between points on the surface lie partially or wholly outside the surface.

Concentric Spheres  -  Spheres that share a common center.

Cone  -  A surface that includes a simple closed curve and the segments that join all the points on that curve with a single fixed point not in the plane of the curve.

Convex Simple Closed Surface  -  A simple closed curve in which a segment joining any two points on the surface lies entirely in the interior of the surface.

Cube  -  A regular polyhedron with six faces, all of which are congruent squares.

Cylinder  -  A geometric surface composed of two congruent simple closed curves lying in parallel planes and segments of parallel lines joining the curves.

Dodecahedron  -  A twelve-faced regular polyhedron whose faces are all congruent regular pentagons.

Edge  -  The intersection of two polygons in a polyhedron.

Face  -  A polygon in a polyhedron.

Geometric Solid  -  A region in space bounded by a closed surface.

Hemisphere  -  Exactly half of a sphere.

Isocahedron  -  A twenty-faced regular polyhedron whose faces are all congruent triangles.

Lateral Edge  -  An edge of a polyhedron, usually refers to a prism or a pyramid.

Lateral Face of a Prism  -  The parallelograms of a prism whose edges are the segments that connect the bases.

Lateral Face of a Pyramid  -  The triangles of a pyramid.

Lateral Surface of a Cone  -  The set of segments that join the base of a cone with its vertex.

Lateral Surface of a Cylinder  -  The set of segments that join the bases of a cylinder.

Octahedron  -  An eight-faced regular polyhedron whose faces are all congruent triangles.

Polyhedron  -  A simple closed surface composed of regions of intersecting planes--these regions are polygons

Prism  -  A polyhedron composed of two congruent polygons that lie in parallel planes and the segments that are part of parallel lines that join the congruent polygons.

Pyramid  -  A polyhedron composed of a polygon and the segments that join that polygon with a fixed point not in the plane of the polygon.

Radius of a Sphere  -  A segment with one endpoint at the center of a sphere and the other endpoint on the sphere.

Regular Polyhedron  -  A polyhedron whose faces are congruent regular polygons

Regular Pyramid  -  A pyramid whose base is a regular polygon and whose altitude intersects the plane of its base at the center of the base.

Right Circular Cone  -  A circular cone whose altitude intersects with the plane of the base at the center of the base.

Right Circular Cylinder  -  A circular cylinder whose lateral edges are perpendicular to the planes that contain the bases.

Right Prism  -  A prism whose lateral edges are perpendicular to the planes of the bases.

Simple Closed Surface  -  A surface that divides space into three distinct regions: 1) points in the interior of the surface, which always form the endpoints of finite segments; 2) points on the surface; and 3) points in the exterior of the surface, which can form the endpoints of infinite segments.

Sphere  -  A surface whose points all lie an equal distance from a fixed point in space.

Surface  -  A geometric figure that traces the motion of a curve in space. A surface is two-dimensional, but can span three dimensions.

Tetrahedron  -  A four-faced regular polyhedron whose faces are all congruent triangles.

Vertex of a Cone  -  The fixed point that is the endpoint of all the segments that form the lateral surface of a cone.

Vertex of a Polyhedron  -  Any point on a polyhedron that is the intersection of three or more faces.

Vertex of a Pyramid  -  The fixed point at the intersection of all the faces of the pyramid.