Polyhedron • A solid that is bounded by polygons, called faces, that enclose a single region of space. • Plural is polyhedral or polyhedrons
Face • One of the flat surfaces that make a polyhedron.
Edge • A line segment formed by the intersection of two faces of a polyhedron.
Vertex • A point where three or more edges of a polyhedron meet.
Base • One of two congruent faces of a polyhedron
Regular Polyhedron • A convex polyhedron in which all of the faces are congruent regular polygons.
Convex Polyhedron • A polyhedron is convex if any two points on its surface can be connected by a segment that lies entirely inside or on the polyhedron. If this segment goes outside the polyhedron, then the polyhedron is nonconvex or concave. convex concave
Platonic Solids • A convex polyhedron where every face is an identical regular polygon
Tetrahedron • A polyhedron with four faces
Cube • A polyhedron with six congruent square faces
Octahedron • A polyhedron with eight faces
Dodecahedron • A polyhedron with twelve faces
Icosahedron • A polyhedron with twenty faces
Cross Section • The intersection of a plane and a solid
Prism • A polyhedron with two congruent faces called bases that lie in parallel planes.
Lateral Faces • The faces of a prism that are parallelograms formed by connecting the corresponding vertices of the bases of the prism
Lateral Edges • The segments connecting the corresponding vertices of the bases of a prism
Surface Area • The sum of the areas of the faces of a polyhedron or other solid
Lateral Area • The sum of the areas of the lateral faces of a polyhedron or other solid with one or two bases.
Net • The two-dimensional representation of the faces of a polyhedron
Right Prism • A prism in which each lateral edge is perpendicular to both bases
Oblique Prism • A prism with lateral edges that are NOT perpendicular to the bases
Cylinder • A solid with congruent circular bases that lie in parallel planes
Right Cylinder • A cylinder in which the segment joining the centers of the bases is perpendicular to both bases
Pyramid • A polyhedron in which the base is a polygon and the lateral faces are triangles with a common vertex
Vertex of a Pyramid • The common vertex of the triangles which make up the lateral faces of a pyramid.
Regular Pyramid • A pyramid that has a regular polygon for a base and in which the segment joining the vertex and the center of the base is perpendicular to the base
Slant Height • The height of a lateral face of the regular pyramid
Cone • A solid that has one circular base and a vertex that is not in the same plane as the base
Vertex of a Cone • The vertex that does not lie in the same plane as the base of a cone
Right Cone • A cone in which the segment joining the vertex and the center of the base is perpendicular to the base. The slant height is the distance between the vertex and a point on the base edge.
Lateral Surface • Consists of all segments that connect the vertex with points on the edge of the base.
Volume • The number of cubic units contained in the interior of a solid
Sphere • The set of all points in space equidistant from a given point called the center of the sphere
Center • The center of a polygon’s circumscribed circle
Radius • A segment whose endpoints are the center of the circle and a point on the circle. The distance from the center of a circle to any point on the circle. • Plural is radii
Chord • A segment whose endpoints are on a sphere
Diameter • A chord that contains the center of a sphere
Great Circle • The intersection of a sphere and a plane that contains the center of the sphere
Hemisphere • Half of a sphere, formed when a great circle separates into two congruent halves
Similar Solids • Two solids of the same type with equal ratios of corresponding linear measures, such as heights or radii