# Avondale Geo 3D

## 38 terms · Unit 4 Vocabulary

### Polyhedron

A solid that is bounded by polygons called faces, that enclose a single region of space.

### Face

The shapes that make up a polyhedron.

### Edge

A line segment formed by the intersection of two faces of a polyhedron

### Vertex

Each endpoint of a side of a polygon

### Regular Polyhedron

A polyhedron whose faces are all congruent regular polygons

### Convex

A polyhedron such that any two points on its surface can be connected by a line segment that lies entirely inside or on the polyhedron.

### Cross Section

The intersection of a plane and a solid.

### Platonic Solids

Five regular polyhedra, named after the Greek mathematician and philosopher Plato, including a regular tetrahedron, a cube, a regular octahedron, a regular dodecahedron, and a regular icosahedron.

### Tetrahedron

A polyhedron with four faces

### Octahedron

A polyhedron with eight faces

### Dodecahedron

A polyhedron with 12 faces

### Icosahedron

A polyhedron with 20 faces

### Prism

A polyhedron with 2 congruent faces called bases, that lie in parallel planes.

### Bases

The two congruent faces

### Lateral Faces

Are parallelograms formed by connecting the corresponding vertices of the bases

### Right Prism

A prism whose lateral edges are perpendicular to both bases.

### Oblique Prism

A prism whose lateral edges are not perpendicular to the bases.

### Surface Area of a polyhedron

The sum of the areas of its faces

### Lateral Area of a polyhedron

The sum of the area of the lateral faces of a polyhedron

### Net

A two-Dimensional representation of all the faces of a polyhedron.

### Cylinder

A solid with congruent bases that lie in parallel planes.

### Right Cylinder

A cylinder such that the segment joining the centers of the bases is perpendicular to the bases.

### Lateral Area of a cylinder

The area of the curved surface of a cylinder.

### Surface Area of a Cylinder

The sum of the lateral area of the cylinder and the areas of the two bases.

### Pyramid

A polyhedron in which the base is a polygon and the lateral faces are triangles with a common vertex.

### Regular Pyramid

A pyramid such that the base is a regular polygon and the segment from the vertex to the center of the base is perpendicular to the base.

### Circular Cone

A solid with a circular base and a vertex that is not in the same plane as the base.

### Lateral Surface of a cone

Consists of all segments that connect the vertex with the points on the edge of a base.

### Right Cone

A cone with a vertex that lies directly above the center of the base.

### Volume of a Solid

The number of cubic units contained in the interior of a solid.

### Sphere

A 3-D form of a circle, has no vertices or edges.

### Center of a sphere

The locus of points in space that are a given distance from a point.

A segment from the center of a sphere to a point on the sphere.

### Chord of a sphere

A segment whose endpoints are on the a sphere

### Diameter of a Sphere

A chord that contains the center of the sphere

### Great Circle

The intersections of a sphere and a plane that contains the center of the sphere

### Hemisphere

Half of the sphere

### Similar Solids

Two solids with equal ratios of corresponding linear measures.