When you should—and should not—use a hyphen

A quick (and probably maddening) guide for using the most exasperating and tiresome punctuation mark of all.

In a previous post, I wrote about the em dash. This gentleman-like punctuation mark is used to indicate a pronounced interruption or break in thought. Now, on to the most exasperating and tiresome punctuation mark of all—the hyphen.

In general, we use hyphens to avoid ambiguity. Otherwise, how would we be able to tell the difference between a “man-eating shark” and a “man eating shark”?

A definitive collection of hyphenation rules does not exist; rather, different style manuals prescribe different usage guidelines. In the style guide that I use most frequently—American Medical Association Manual of Style—there are eight pages on the hyphen. These pages include rules for when to use hyphens and when not to use them.

Hyphenation rules can be exceedingly complicated. Byzantine even. (I want to write, not solve differential equations.) I once spent 30 minutes explaining to someone why “work up” is hyphenated in some instances, but not others.

Hyphens connect words, prefixes, and suffixes permanently or temporarily. When not otherwise specified, hyphens should be used only to avoid ambiguity. What follows is an abridged version of the hyphenation rules taken from the AMA Manual of Style. Other style guides will have different rules, but this is a place to start.

Hyphenate when the terms are used as an adjective before the noun.

• Did the creators of hyphenation rules use valid decision-making methods? (But: Their methods of decision making were questionable.)
• The student came for a follow-up visit to discuss his inability to hyphenate correctly. (But: Be sure to follow up with that style guide.)

Hyphenate two nouns of equal participation used as a single noun.

• She is a writer-editor.
• The student-teacher relationship became strained once the rules for hyphenation were introduced.

Use a hyphen as a prefix when the unhyphenated word would have a different meaning.

• re-treat
• re-creation
• re-formation

(After all, a reformed rock band is different from a re-formed rock band.)

Hyphens can also be used to avoid an awkward combination of letters.

• de-emphasize
• anti-inflammatory

Just in case you weren’t confused enough, here are the rules for when not to use a hyphen. The following common prefixes are not joined by hyphens:

• ante (antebellum)
• anti (antibiotic)
• bi (bivalve)
• co (coauthor)
• contra (contraindication)
• de (debrief)
• extra (extracurricular)
• infra (infrared)
• inter (interoperatively)
• intra (intravenous)
• micro (microsurgery)
• mid (midway)
• non (noncompliant)
• over (overtreatment)
• pre (preoperatively)
• post (postoperatively)
• pro (proactive)
• pseudo (pseudoscience)
• re (retrench)
• semi (semiannual)
• sub (substandard)
• super (supernatural)
• supra (suprapubic)
• trans (transaortic)
• tri (triglycerides)
• ultra (ultrasound)
• un (unconscious)
• under (underbite)

An old Oxford University Press style guide once offered the following sage advice: “If you take hyphens seriously you will surely go mad.” If this post doesn’t at least set you on the road to madness, then you weren’t paying attention.

A version of this story first appeared on the author’s blog Impertinent Remarks.


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