Having explored the uses of the em-dash and the en-dash, we now come to the most commonly known of the dash punctuation marks: the hyphen.
The hyphen’s main job is to connect two or more things that are closely related, usually words that work together as a single concept (a compound term), or that serve as a joint modifier (a phrasal adjective).
Put simply, a compound term is a term formed by more than one word.
Some compound terms are written as two separate words, such as living room and post office. These are called “open compounds.”
Others are hyphenated, like father-in-law and over-the-counter.
And then there are those we write as a single word, such as fireworks and upstream.
Grammarians say that compound terms often enter the lexicon as two separate words, such as hard drive.
After some time, they may become hyphenated, like freeze-dried.
When the term becomes commonplace, it often solidifies into one word, such as moonlight (and, for that matter, commonplace). “The steady evolution of the language seems to favor union,” observe Strunk and White in The Elements of Style, 3rd ed.
If you are uncertain how a compound term should be written, consult a dictionary or usage guide.
When two or more words work together as a single modifier, or “phrasal adjective,” as legal writing expert Bryan Garner puts it, they should usually be joined by hyphens.
We do this so that the reader can easily distinguish the nouns from the adjectives.
Here’s an example from Richard Wydick’s Plain English for Lawyers, 5th ed. of a sentence where a failure to hyphenate creates confusion: “The new tax deduction is designed to aid small business owners.”
Does that mean that the large ones must fend for themselves? Most likely, the writer is speaking of small-business owners, and not owners who are small in physical stature.
Here’s a phrase Garner uses in The Elements of Legal Style, 2nd ed. to show how a lack of hyphenation can result in a lack of clarity: common law mirror image rule. The problem, he notes, is that the reader is most likely to initially see common law as the noun—not realizing that the true noun is rule.
We can lessen the reader’s burden if we write it this way: common-law mirror-image rule.
Only hyphenate when the phrasal adjective comes before the noun: hard-hearted Hannah, as opposed to, “Hannah is hard hearted.”
Also, do not hyphenate when the first word is an adverb ending in -ly, as in, a radically different design.
And where two or more hyphenated compound terms share the same word, you can use the shared word just once if you write the phrase like this: Long- and short-term financial planning.
Note the space that appears between the word, and, and the hyphen after the word, long.
We have other uses for the hyphen, such as to demarcate the groupings of a phone number, e.g., 867-5309. We do not use an en-dash in those circumstances, because we are not indicating a range of numbers.
Garner and Wydick point out that some prefixes are almost always followed by a hyphen, such as ex-, self- (when joined to a word and not a suffix), quasi-, and all-.
Otherwise, do not place a hyphen between the prefix and the base word, unless one is required to stave off confusion, e.g., pre-judicial (as opposed to prejudicial), or to avoid what Garner calls a “visual monstrosity,” e.g. multi-institutional.
Wydick also advises using hyphens when writing out numbers twenty-one through ninety-nine, even when they are part of a larger number, as in two hundred and forty-six.
Finally, don’t forget to place a hyphen between all elements of a fraction acting as a compound adjective, e.g. a one-twenty-sixth share.
Since the proper use of hyphens can be confusing, Garner recommends keeping a list handy of the preferred spellings of compound terms that repeatedly foul you up and entering them in your computer’s spell-check dictionary if they come up as errors.
About the author:
Savannah Blackwell is a former news reporter who covered government and politics in San Francisco for more than a decade and is now Of Counsel at Renne Public Law Group. She can be reached at firstname.lastname@example.org. Follow her on Twitter at @SavannahBinSF.