     ## NAMING POLYGONS

Naming a polygon by its number of sides requires that we know the appropriate Greek prefixes along with some rules for their use.
 3 = tri 4 = tetra 5 = penta 6 = hexa or sexa 7 = hepta 8 = octa 9 = nona or ennea 10 = deca 11 = undeca or hendeca 12 = dodeca 13 = triskaideca 14 = tetradeca 15 = pentadeca 16 = hexadeca 17 = heptadeca 18 = octadeca 19 = enneadeca 20 = icosa
For polygons with 3 through 20 sides, simply add "gon" to the prefixes at the left (although a trigon is more commonly called a triangle and a tetragon, a quadrilateral!).

For more than 20 sides, we "construct" the name by using so-called combining prefixes:

 Tens Digit 20 = icosi 30 = triaconta 40 = tetraconta 50 = pentaconta 60 = hexaconta 70 = heptaconta 80 = octaconta 90 = enneaconta
 Ones Digit 1 = hena 2 = di 3 = tri 4 = tetra 5 = penta 6 = hexa 7 = hepta 8 = octa 9 = ennea
3 - 99 SIDES
To "construct" a name, we start with the prefix for the tens digit, follow it by "kai" (the Greek word for "and"), then follow it with the prefix for the units digit, and finally add "gon."

Example: A 35-sided polygon is called a "triacontakaipentagon."

 30 and 5 gon triaconta kai penta gon

100 - 999 SIDES
For numbers from 100 to 999, we need one more combining prefix and another rule.

To "construct" the name, we start with the prefix for the hundreds digit taken from the "Ones Digit" table above, follow it by "hecta," then proceed as before.

Example: A 672-sided polygon is called a "hexahectaheptacontakaidigon."

 100 = hecta
 600 70 and 2 gon hexa + hecta heptaconta kai di gon

 Now you try some. When you think have the name, click on the ANSWER button to check. 83 sides 257 sides 999 sides  