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### Prefixes in Math

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Date: 08/21/2001 at 21:13:30
From: anthony

What are the prefixes for 7, 8, 9, and 10?

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Date: 08/22/2001 at 09:23:24
From: Doctor Peterson

Hi, Anthony.

Which prefixes are you referring to?

There are actually at least two sets of number prefixes in English,
derived from Latin and Greek. The Latin are used (a little modified)
in names for large numbers:

Large Numbers and Infinity - Dr. Math FAQ
http://mathforum.org/dr.math/faq/faq.large.numbers.html

Decillion, Vigintillion, Trigintillion... - Dr. Math Archives
http://mathforum.org/dr.math/problems/trichardt12.10.98.html

The Greek forms are used in names of polygons:

Naming Polygons and Polyhedra - Dr. Math FAQ
http://mathforum.org/dr.math/faq/faq.polygon.names.html

Here is a list of them:

Number   Greek        Latin
------   -----        -----
1     mono-        uni-
2     duo-/di-     duo-/bi-
3     tri-         tri-
5     penta-       quint-
6     hex-         sex-
7     hept-        sept-
8     oct-         oct-
9     ennea-       non-
10     dec-         dec-
20     icosa-       vigint-
30     triaconta-   trigint-
50     pentaconta-  quinquagint-
60     hexaconta-   sexagint-
70     heptaconta-  septuagint-
80     octaconta-   octogint-
90     enneaconta-  nonagint-
100     hect  -      cent-

I haven't found all of these in dictionaries; the higher ones are
taken straight from Latin or Greek rather than from standard English
prefixes, and many have several variants. (You can find the teens in
the pages I cited.)

You may enjoy looking them all up in a dictionary to see what words
use them.

- Doctor Peterson, The Math Forum
http://mathforum.org/dr.math/
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Associated Topics:
Elementary Large Numbers