The practice of writing out (and writing about) numbers on Wikipedia follows many of the same rules readers see in newspapers. For instance, writers should spell out whole numbers between zero and nine, but numbers 10 and above use numerals. (There are exceptions, of course!)

Here are a few simple rules to keep in mind when dealing with numbers:

  • Avoid beginning sentences with numerals

  • People's ages are always written as numerals

  • Use hyphens when spelling out fractions ("two-thirds")

  • Numbers greater than 10 that are one or two words long can be spelled out ("six hundred")

  • Spell out out million and trillion, but M and bn are acceptable following numerals on subsequent uses

  • Decimals contain periods, not commas (so U.S. style wins here)

  • Use numerals in tables and infoboxes

  • Use numerals when discussing percents, and use "percent", not %

Now you know! Next week, a related subject: dates and times.