A base-2 number system is called binary and a base-10 system decimal, but what how does one term number systems based on 3, 4, 5, 8 or 12 ? This is a question that I had to answer in 1999 March, so I did some research, and below are (almost all of) my findings. Please inform me of errors that I have made or of additions that you would like to make via email.
| Base | Name |
| 2 | binary |
| 3 | ternary [A] |
| 4 | quaternary |
| 5 | quinary |
| 6 | senary |
| 7 | septenary |
| 8 | octonary [B] |
| 9 | nonary |
| 10 | decimal |
| 11 | undenary |
| 12 | duodecimal |
| 13 | tridecimal |
| 14 | quattuordecimal |
| 15 | quindecimal |
| 16 | sexadecimal [C] |
| 17 | septendecimal |
| 18 | octodecimal |
| 19 | nonadecimal |
| 20 | vigesimal |
| 30 | trigesimal |
| 40 | quadragesimal |
| 50 | quinquagesimal |
| 60 | sexagesimal |
| 70 | septagesimal |
| 80 | octagesimal |
| 90 | nonagesimal |
| 100 | centimal |
| 200 | bicentimal |
| 300 | tercentimal |
| 400 | quattrocentimal |
| 500 | quincentimal |
| [A] | Also “trinary”. |
| [B] | Most commonly “octal” but also “octonal” or “octimal”. |
| [C] | “hexadecimal” is the common computer-science terminology, but it is unsatisfactory because it is a combination of the Greek “hexa” and the Latin “decim”. The proper Latin should be “sedecim” or “sexdecim”, yielding either “sedecimal” or “sexadecimal”. Schwartzman writes: “Since hexadecimal is a rather long word, it is sometimes abbreviated hex. The word hexadecimal is unusual because Greek and Latin elements are combined; the expected purely Latin form would be sexadecimal, but then computer hackers would be tempted to shorten the word to sex.” [emphasis added] |
Schwartzman S (1994). The Words of Mathematics: an etymological dictionary of mathematical terms used in English (ISBN 0-88385-511-9).