• ### 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.