Crimes of Innumeracy

“Innumeracy” isn't in the dictionary. The word comes from the title of a book by John Allen Paulos, Innumeracy: Mathematical Illiteracy and Its Consequences.

Writing numbers	Whether to use words or numerals, and all about the suffixes on ordinal numbers.
Phone numbers	Strip out the unnecessary stuff.
The year 2000	Why do people say "the year 2000" but just "1999"?
Things that cost less than a penny	A decimal point and a cent sign signify a ridiculous sale.