Hyphens, En Dashes, Em Dashes

Q. Please help! My British colleagues keep giving me books to proofread (for US publication, so they should be in American style) in which phrases like “parent-teacher relationship” and “human-animal bond” contain an en dash rather than a hyphen. Chicago says that if either “parent” or “teacher” were an open compound (such as, I suppose, “math teacher”), an en dash would be appropriate—so am I to conclude that since this is not the case I should use a hyphen? As far as I can tell, none of the examples in the section on hyphenation pertain to this construction. Are the en dashes correct, or are they just British?

A. Your British colleagues might be following Butcher’s Copy-editing: The Cambridge Handbook for Editors, Copy-editors, and Proofreaders , 4th ed. (Cambridge: Cambridge University Press, 2006), which advises using what it calls “en rules” “to convey a distinction in sense” (section 6.12.1; note that it is also the common British practice to use an en dash with a word space on either side where American publishers would use an em dash closed up to the surrounding words). This allows one to write, for example, “US–British relations” to mean relations between the United States and Britain. The en dash is supposed to convey something more than simply relations that are characterized or modified, independently, by the United States and Britain. And while editors here like such a subtle distinction, we do not believe that it is useful enough to mandate, and therefore we prefer the hyphen (e.g., US-British relations). En dashes instead of hyphens should be used between words in running text only as a last resort—usually to bridge an open compound, as you suggest—and even then it’s probably fair to assume that most readers will see a hyphen.