I've written more than once about hyphens, including this post, but it remains a troublesome topic, so I'll approach it from this direction, too: the categories of hyphenation errors.
1. Omitting hyphens in phrasal adjectives
Some phrasal adjectives (including "civil rights," "stock
market" and "high school") don't require hyphenation when they appear
before a noun; they're so well entrenched in the language that no risk
of ambiguity exists, and their status is enshrined by inclusion in
But when two words team together to describe a noun, they're
usually hyphenated. (Leave them open after a noun, however.) If you
can't find them in your well-thumbed dictionary, attach them—and don't
hesitate to link more than two words: "The company instituted a
2. Adding hyphens to compound words
Compound words come in three forms: open (sand dollar), hyphenated (sand-blind), and closed (sandbag).
As you see from these examples, compounds including the same particular
word are not necessarily treated the same; compounding is a random
process related to usage.
Popular treatment of long-hyphenated compounds changes so
rapidly that dictionaries change them in new editions to reflect
prevailing usage; pigeonhole—formerly pigeon-hole—is just one example.
3. Adding hyphens to prefixes
Prefixes, on the other hand, are almost always closed up to
the root word. Exceptions include when the root word is a proper name (pre-Christian) and when the prefix ends and the root word begins with an i (anti-inflammatory).
Note, however, that this is not true in the case of e
(preempt). Another exception is words beginning with c preceded by co-,
because to many people, terms like co-chair look awkward without a hyphen.
4. Omitting hyphens from potential homographs
Sometimes, prefixed words that would otherwise be closed up
retain a hyphen to distinguish them from otherwise identical-looking
words, such as re-cover as opposed to recover and re-creation as distinct from recreation.
5. Omitting hyphens in verb phrases
Compound verbs, those consisting of more than one word, are hyphenated (test-drive) or closed (troubleshoot);
the dictionary will let you know which form to employ. Note, however,
the difference in nearly identical-looking compound verbs and open
compound nouns: "I'm going to test-drive it tomorrow," but "I'm going to
take it on a test drive tomorrow."
Also, consider the subtle difference between gerunds formed
from a hyphenated compound verb that are followed, or not followed, by
an object: "I was spot-checking the report when I found a serious
error," but "I'm going to do a little spot checking."
6. Adding hyphens to adverbial phrases
Adverbs are not attached to adjectives when they team up to
modify a noun: "The slowly melting ice rendered the river crossing a
perilous enterprise." However, the presence of an adverb does not negate
the need for a hyphen in a phrasal adjective that follows it: "Hers was
an eloquently sharp-tongued response."
7. Adding hyphens to prepositional phrases
Phrases telling the reader to do something in which the
first word is a verb and the second is a preposition are not hyphenated:
"Sign in at the registration table." (The phrase is hyphenated,
however, when it modifies a noun: "Go to the sign-in table.")
8. Adding or omitting hyphens when referring to ages or physical dimensions
When a person is identified by their age with the phrase
"seven-year-old," for example, the phrase is hyphenated whether it
modifies child, boy, girl, and so on or the
noun is implied. (Note that two hyphens are necessary and that, for the
spelled-out form of a two-digit number, three are required:
"twenty-seven-year-old.") However, the constituent words are unattached
when the phrase follows the noun: "The child is seven years old.
By the same rules, words describing an object's physical
dimensions are similarly linked: "Cut the eight-foot-long board in
half." Note, again, that all the words describing the length of the
board are attached: If the final hyphen is incorrectly omitted, the
reference to a board that is eight feet long is erroneously changed to
describe a long board with eight feet.
9. Omitting letter spaces when using hyphens
When you see a hyphen followed by a letter space, don't assume the space is an error.
"The assignment is a 2,000- to 5,000-word essay" is correct;
word has been omitted after the first number because it is implied by
its presence after the second number. (This usage is called suspensive hyphenation.)
10. Confusing hyphens and dashes
Many publications, for the sake of simplicity or because the
producers don't know any better, use single hyphens in place of em
dashes or double hyphens (the less aesthetically pleasing alternative
that is frequently employed online). But they look stubby and ugly, and
this crime against aesthetics is compounded when letter spaces around
them are omitted, producing abominations such as "The key-and this is
important-is to keep stirring constantly."
A version of this article ran on DailyWritingTips.com.