Polyhedra and Non-Polyhedra

polygon

A closed, plane figure formed by three or more line segment

octagon

A eight-sided polygon

pentagon

A five-sided polygon

quadrilateral

A four-sided polygon.

nonagon

A nine-sided polygon

triangle

A polygon with three sides.

heptagon

A seven-sided polygon

hexagon

A six-sided polygon

decagon

A ten-sided polygon

dodecagon

A twelve-sided polygon

regular polygon

a polygon with congruent sides and congruent angles

irregular polygon

a polygon with incongruent sides and incongruent angles

geometric solid

a three-dimensional shape

congruent

equal

face

flat surface on a geometric solid

polyhedron

solid bounded by polygons

non-polyhedron

solid with round surfaces

vertex

the point where two lines (on a polygon) or three faces (on a geometric solid) intersect

edge

the segment where two faces on a geometric solid intersect

perimeter

the sum length around a polygon

net

two-dimensional pattern of a three-dimensional figure; can be folded into a geometric solid