Geometry--3-D Figures Vocabulary

Solid

A three-dimensional object.

Unit Cube

A cube that has a side length of 1 unit.

Face

A flat two-dimensional side that forms a surface of a polyhedron.

Edge

The one-dimensional line segment. where faces meet.

Vertex

The point where edges meet.

Polyhedron

A closed solid made up entirely of faces, edges, and vertices.

Orthographic view

A two-dimensional diagram from a perspective perpendicular to a face that, along with two other orthographic views, can communicate the size and shape of many three-dimensional solids.

Isometric view

A drawing of a solid in which the lines along any axis remain parallel and proportionate to one another, but the axes are not orthogonal to one another.

Cross section

The face formed by the intersection of a plane that slices through a solid.

Uniform cross section

This occurs when a cross section is parallel to the base of a solid and has the same size and shape as the base, that cross section.

Prism

A polyhedron with two congruent polygonal sides connected by parallelograms.

Base

The congruent polygonal sides of a prism.

Lateral faces

The sides connecting the bases.

Lateral edge

The 1-D intersection of two lateral faces.

Base edge

The 1-D intersection of a lateral face and a base.

Height

The distance between the bases of prism.

Cylinder

A 3-D solid with circular bases connected by one curved surface.

Axis

The line segment connecting the centers of the circular bases.

Lateral Area

the combined area of all the lateral faces. The symbol is L.

Net

A diagram of 3-D polygons joined at edges, which can be folded along the edges to construct the solid.

Surface area

The sum of the areas of the lateral faces and the bases. The symbol is S.

Pyramid

A 3-D closed figure such that the base is a polygon, and the lateral faces are triangles with a common vertex.

Apex

The common vertex of a pyramid.

Slant height

The altitude or height of a lateral face.

Regular pyramid

A pyramid, in which, the base is a regular polygon, the lateral edges are congruent, the lateral faces are congruent isosceles triangles, and the slant heights are congruent.

Cone

A 3-D closed figure with a circular base and one vertex.

Right cone

A cone whose vertex is aligned directly above the center of its base.

Oblique cone

A cone whose vertex is not aligned directly over the center of its base edge.

Sphere

A perfectly round, 3-D, ball shaped object.

Hemisphere

Half of a sphere.

Composite solid

A 3-D object made from two or more 3-D solids.

Similar solids

These solids have the same shape, and the ratios of their corresponding linear measures are equal.

Congruent solids

These solids have the same shape and size. They have congruent corresponding angles, edges, and faces, and equal volumes.