# Base ten is called “decimal”; what's the name of numbers in base 15?

Good afternoon all, I was wondering is there a table of names for the base x of numbers?

For example, I know that numbers in base 10 are called "decimal", those in base 2 are called "binary", base 16 is called "hexadecimal", but what will be the name for those in base 9, or base 15 ?

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it has no real name you could expand the latin (or was it greek?) to other numbers (pentadecimal) but I doubt it will catch on, no-one uses base 15 or base 9 enough for it to get a name – ratchet freak Jan 23 '12 at 14:07
See other bases in human language. Also, I give lessons on how to use Google... – The Chaz 2.0 Jan 23 '12 at 14:07
I have heard the term quindecimal but looking in Google now shows that (although it can be used for base 15) it is primarily used for a certain 15-note musical scale. – GEdgar Jan 23 '12 at 14:32
About typography: please omit the hyphen after "base"; in that position it could be taken (as I did) for a minus sign. Positional number systems with negative bases do exist! – Marc van Leeuwen Jan 23 '12 at 14:38
Your title should say "base 2" or "base two" in reference to binary, not "base 10" (which ordinarily means "base ten"); i.e., "base 10" is not ordinarily called "binary". – r.e.s. Jan 23 '12 at 15:18

## 1 Answer

Nonary and pentadecimal respectively.

You might also be interested in the Wikipedia articles that give the names for n-ary bases and the article on radix, which is another name for 'base'.

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There's a convention that when new words are coined, one doesn't mix Latin with Greek. This is sometimes violated, e.g., in "automobile," where "auto-" is Greek but "-mobile" is Latin. But since GEdgar points out that quindecimal does have some currency, that would be a reason to prefer quindecimal rather than pentadecimal. Here is some information about Greek and Latin number prefixes: en.wikipedia.org/wiki/Number_prefix Google ngram viewer books.google.com/ngrams shows zero hits for both words in books since 1800, which suggests that there simply isn't a commonly accepted word. – Ben Crowell Jan 23 '12 at 18:13
@BenCrowell I'd err slightly in the other direction, for two reasons: (a) 'pentadecimal' is consistent with 'hexadecimal' which also mixes Greek and Latin, and (b) a Google verbatim search shows five times more hits for 'pentadecimal' than for 'quindecimal'. But I agree that there is little consensus, and for that reason it probably doesn't matter which you use. As an aside, my favourite example of a mixed Greek-Latin root is 'television' :) – Chris Taylor Jan 23 '12 at 18:33
And also polyamory. That's why polyamory is wrong. – Michael Hardy Jan 24 '12 at 0:33