Numerical Prefixes

The Greek numerical prefixes are used for naming things like polygons, polyhedra and polynomials::

mono = 1
di = 2
tri = 3
tetra = 4
penta = 5
hexa = 6
hepta = 7
octa = 8
ennea = 9
deca = 10
hendeca = 11
dodeca = 12
triskaideca = 13
tetrakaideca...enneakaideca = 14...19
icosa = 20
icosikaihena = 21
icosidi...icosiennea = 22...29
triaconta = 30
tetraconta...enneaconta = 40..90
hecto | hecato = 100
chilia = 1000
myria = 10000

The word "kai", meaning and, is often omitted. Chemistry uses a slightly different set of prefixes, two of which come from latin::

nona = 9
undeca = 11

And the rest of which are pretty much made up::

henicosa = 21
docosa...nonacosa = 22...29
hentriaconta...nonatriaconta = 31...39
kilia = 1000
dilia...nonalia = 2000...9000

And, finally, for large numbers these prefixes are used:

bi = 2
tri = 3
quadra = 4
quinta = 5
sexta = 6
septa = 7
octo = 8
nona = 9
deca = 10
undeca = 11
dodeca = 12
tredeca = 13
quattuordeca = 14
quinquedeca = 15
sexdeca = 16
septendeca = 17
octodeca = 18
novemdeca = 19
viginti = 20
unviginti...novemviginti = 21...29
triginti = 30

Some of these suffices need checking, since these are not quite the latin names of the numbers...but in the actual compounds (e.g. octillion, vigintillion) they disappear.