Sometimes readers ask for posts that would require superhuman powers on my part:
Kindly produce an article containing all the exceptions for hyphenating compound adjectives, with examples.
Hyphenation is not an exact science, and not all style guides agree on the rules. The chief purpose of hyphenating compound adjectives is to avoid ambiguity.
Most modern usage authorities opt for what The Chicago Manual of Style calls “a spare hyphenation style”:
7. Spelling, Distinctive Treatment of Words, and Compounds
In general, Chicago prefers a spare hyphenation style: if no suitable example or analogy can be found either in this section or in the dictionary, hyphenate only if doing so will aid readability.
When Grammar Girl was chided for writing “noise canceling headphones” instead of “noise-canceling headphones,” she pointed out that leaving out the hyphen in that phrase “causes no ambiguity.”
When one of my own readers called my attention to the unhyphenated phrase “19th century standardization of time” in a recent post, I decided to change it to “nineteenth-century standardization of time”—not because I think it ambiguous without a hyphen, but because Chicago is the style guide I’ve chosen for these posts. I failed to note that Chicago offers an analogy for hyphenating nineteenth-century before a noun: fourteenth-century monastery (7.85).
Note: Chicago recommends spelling out numerals below 100, so I must also change 19th to nineteenth. The AP Stylebook, on the other hand, requires the spelling out of numerals ten and below. For AP, 19th century is correct. Still another stylebook,
The Blue Book of Grammar and Punctuation) offers this advice about hyphenating constructions like “nineteenth century standardization”:
As important as hyphens are to clear writing, they can become an annoyance if overused. Avoid adding hyphens when the meaning is clear. Many phrases are so familiar (e.g., high school, twentieth century, one hundred percent) that they can go before a noun without risk of confusing the reader.
a high school senior
a twentieth century throwback
one hundred percent correct
Because practice varies, I wouldn’t begin to attempt to list “all the exceptions for hyphenating compound adjectives.”
The best advice I can offer the reader who asked for such a list is this: Choose a style guide and follow its recommendations—advice I shall try to follow more carefully in future posts.