**
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.