Today, in honor of Better Business Communication Day, we're sorting through the stacks of (differently sized) business stationery. (来源：www.EnglishCN.com)

Americans have two usual sizes for paper: letter size, measuring 8 and 1/2 by 11 inches; and legal size, measuring 8 and 1/2 by 14 inches. What we know as legal size, our British cousins call foolscap. Foolscap was once the paper standard in Great Britain; its name comes from the onetime practice of applying a watermark picturing a fool's cap on the paper. And the British term for letter size paper is quarto, the ablative form of the Latin fourth, which recognizes the fact quarto pages are cut four to a sheet.

But being able to distinguish quarto from foolscap is not enough. Can you explain where European A4 papers fit into the picture? Measuring 8 and 1/4 inches wide (a tad narrower than the previously mentioned sheets of paper) by 11 and 3/4 inches long (three quarters of an inch longer than letter size), this is the standard business stationery used outside the U.S.

Why the different sizing? According to the ISO, the International Organization for Standardization, A4 papers follow the rule that the height of a paper divided by its width will yield the square root of two. That makes for less waste and more utility for many printing jobs.