Crimes of Innumeracy

Writing numbers

when to spell them out and when to use numerals

Usually, write out numbers under 10 and use numerals for numbers 10 and over.

However, use numerals in "section 3," "item 6," "the number 8," and other such cases.

where to put the "th" in ordinal numbers

Well, if the number is less than 10, then it's at the end of the word ("third," "fifth," "eighth"). If the number is 10 or more, then it's immediately after the number, in the same font size and with the same baseline. Thus, write "15th," not "15^th." I dislike roller coasters, even when I'm reading. (Coming soon to a Web site near you: instructions on disabling all the nasty default formatting - such as the "th" problem - that appears when you install Microsoft Word.)

whether it's "d" or "nd" and "rd"

For those ordinal numbers that end in 2 or 3, newspapers tend to prefer "d" rather than "nd" and "rd" as the suffix. I do too, because it's shorter. However, there's nothing wrong with either "23d" or "23rd."

fractions

If the numerator and the denominator are each less than 10 and there's no integer before the fraction, write it out and use a hyphen in between the numerator and the denominator. If there's an integer part or the numerator or the denominator is 10 or greater, use numerals. (And don't put a "th" after the number.)

Thus, it's one-half, two-thirds, ²²/₇, 1¹/₂, and ¹/₁₆ - not "¹/₁₆th."