Hyphens are undoubtedly confusing to many people—hyphen problems are now one of the twenty most common surface errors in student writing (see p. 11). The confusion is understandable. Over time, the conventions for hyphen use in a given word can change (tomorrow was once spelled to-morrow). New words, even compounds such as firewall, generally don’t use hyphens, but controversy continues to rage over whether to hyphenate email (or is it e-mail?). And some words are hyphenated when they serve one kind of purpose in a sentence and not when they serve another.