Naming Polygons
HOMEWORK: Complete ‘Name That
Polygon’ Activities WS
Naming a polygon by its number of sides requires
that we know the appropriate Greek prefixes along
with some rules for their use.
For polygons with
3 through 20
sides, simply add
"gon" to the prefixes to
the right 
- although a trigon is
more commonly called a
triangle and a tetragon,
a quadrilateral!
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
tri
tetra
penta
hexa or sexa
hepta
octa
nona
deca
undeca
dodeca
triskaideca
tetradeca
pentadeca
hexadeca
heptadeca
octadeca
enneadeca
icosa
21 - 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
For more than 20 sides, we "construct" the
name by combining prefixes:
20
30
40
50
60
70
80
90
Tens Digit
= icosi
= triaconta
= tetraconta
= pentaconta
= hexaconta
= heptaconta
= octaconta
= enneaconta
+
1
2
3
4
5
6
7
8
9
=
=
=
=
=
=
=
=
=
Ones Digit
hena
di
tri
tetra
penta
hexa
hepta
octa
ennea
25 = icosi + kai + penta+ gon = icosikaipentagon
77 = heptaconta + kai + hepta + gon = heptacontakaiheptagon
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 =
600
hexa + hecta
70
heptaconta
hecta
and
kai
2
di
gon
gon
Now you try some
914 sides
75 sides
753 sides
Triskaidecagon
13
Tetrakaidecagon
14
Pentadecagon
15
Hexakaidecagon
16
Heptadecagon
17
Octakaidecagon
18
Enneadecagon
19
Icosagon
20
Triacontagon
30
Tetracontagon
40
Pentacontagon
50
Hexacontagon
60
Heptacontagon
70
Octacontagon
80
Enneacontagon
90
Hectagon
100
Chiliagon
1,000
Myriagon
10,000
Megagon
1,000,000
Googolgon
10100
Hectagon
100
Chiliagon
1,000
Myriagon
10,000
Megagon
1,000,000
Googolgon
10100
How many sides??
Tetracontakaihexagon
Icosikaioctagon
Octacontakaihexagon
Heptacontakaitrigon
Octacontakaitrigon
Dihectapentacontakaiheptagon
Enneahectaenneacontakaienneagon