gon-, gonio-, -gon, -gonal, -gonally, -gony

(Greek: corner, bend, angle)

agonic (adjective), more agonic, most agonic
Characteristic of not forming an angle; having no angle: The line indicating the perimeter of a circle is an agonic line.
decagon
diagon
diagonal (adjective) (not comparable)
Pertaining to a straight line or mark that extends at an angle, and not straight up and across: The geometry teacher, Mr. Tall, told his students to draw a diagonal line linking the opposite corners of the square pictured on their worksheets.

The jogging pants that Susan bought had bright red diagonal stripes.

dodecagon
enneagon
goniometer
goniometry
hendecagonal (adjective), more hendecagonal, most hendecagonal
In the form or in the shape of a multiple angles having eleven sides.
heptagon (s) (noun), heptagons (pl)
A geometric shape with seven angles and seven sides: "The students were learning about heptagons in their math class."
hexagon
isogonic
Having , or pertaining to, equal angles.
nonagon, nonagonal; enneagon
A polygon having nine angles and nine sides.
octagon
orthogonal
1. Having or determined by right angles; perpendicular.
2. An area of a computer display in which units of distance are the same horizontally and vertically so that there is no distortion.