A job listing I read last spring asked for "a detail oriented, self starting candidate with a customer first attitude." Nothing in that sentence is ungrammatical. It still reads like a telegram, and the writer had no idea why anyone would notice.
Then there is the opposite habit, where a careful writer hyphens every compound in sight and produces sentences that look nervous: "The author is well-known." Both problems come from one missing rule.
The rule that fixes most of it
Hyphenate a compound modifier when it comes before the noun. Leave it open when it comes after.
| Before the noun | After the noun |
|---|---|
| a well-known author | the author is well known |
| a last-minute decision | the decision was last minute |
| a high-risk investment | the investment is high risk |
| a full-time job | she works full time |
| a ten-year-old car | the car is ten years old |
The reason is competition. In "a last minute decision," the words are still strangers to each other, and a reader can briefly parse the phrase as a decision about a minute that happens to be last. Move the modifier after the noun and the verb "is" does the binding for you. "The decision was last minute" cannot be misread.
That single sentence settles most hyphen arguments in a manuscript. Ask whether the compound sits before or after the noun and the answer usually arrives on its own.
Two exceptions worth knowing
Adverbs ending in -ly never take a hyphen, even before a noun. Write "a highly effective method," "a newly painted fence," "a carefully worded email." The -ly already signals that the adverb modifies what follows.
Established compounds do not need one either: "a real estate agent," "an income tax return," "a high school student." The hyphen exists to prevent a misreading, and where no misreading is possible, the mark has no work to do.
Suspended hyphens: one mark, two jobs
When two compound modifiers share a final word, the hyphen can hang in place while the shared part is dropped.
two- and three-day trips
a mix of long- and short-form content
first-, second-, and third-place winners
That construction saves repetition. It also has one detail that catches people: the space after the suspended hyphen. "Two- and three-day trips" puts a space between the hyphen and "and." Without it, "two-and three-day" reads like a typo.
The same trick works with numbers.
a 5- and 10-year plan, not a 5 and 10-year plan
The hyphen is not a dash
Writers confuse these constantly, and the difference is not decorative.
| Mark | Rough width | Job | Example |
|---|---|---|---|
| Hyphen (-) | shortest | joins words into a single unit | a well-known author |
| En dash | about the width of a lowercase n | ranges, spans, scores | pages 40–50 |
| Em dash | about the width of a capital M | an interruption or an aside | I was going to—anyway. |
A hyphen binds. A dash separates. The two marks pull in opposite directions, which is why a hyphen used to interrupt a sentence looks wrong even to a reader who cannot explain the rule. The full guide to dashes covers the en and em dash in their own right; here the point is simply that compounds take a hyphen and interruptions do not.
One practical note: word processors convert a double hyphen into an em dash automatically, so a stray dash inside a compound is usually autocorrect rather than a typo.
Compounds that close up over time
Compounds begin life hyphenated and gradually fuse. Readers stop needing the seam marked, and the mark disappears.
| Then | Now, for most US publishers |
|---|---|
| web site | website |
| on-line | online |
| co-ordinate | coordinate |
| data base | database |
Nothing about the language changed; habit changed. "E-mail" was standard in the 1990s and now looks dated, and most British publications have followed American practice and adopted "email" as well. Some compounds resist the trend: "well-being," "self-esteem," and "e-book" keep their hyphens in most current style guides.
This is where house style beats general rules. If your publication writes "email," it writes "email" everywhere. Ten minutes spent recording those decisions in a style sheet saves an argument every time a new writer joins.
Numbers, units, and ages
When a number and a unit work together as a modifier, the whole unit takes hyphens.
a 30-year mortgage
a 6-foot ladder
a 90-minute flight
a 40-hour work week
a five-dollar bill
Move the measurement out of modifier position and the hyphens go with it. "The mortgage runs 30 years." "The ladder is 6 feet tall." "The flight takes 90 minutes." The phrase has stopped being a single adjective, so the glue comes off. The guide to numbers in writing covers when to use digits and when to spell a number out, and that answer varies by style guide. The hyphen does not: "a 30-year mortgage" and "a thirty-year mortgage" are both correct and both hyphenated.
Fractions keep their hyphen in every position: "two-thirds of the budget," "a two-thirds majority." Ages follow the compound rule, so a child is "three years old" and also "a three-year-old."
Where the hyphen prevents a misreading
Every case above is about clarity. These are about meaning.
A small business owner. Without the hyphen, this could describe an owner who is small, or the owner of a small business. "A small-business owner" removes the ambiguity.
Man eating shark. A "man-eating shark" is a shark that eats people. Drop the hyphen and the phrase describes a person having dinner.
Twenty-odd people. The hyphen means roughly twenty. Remove it and "twenty odd people" means twenty strange people.
Re-sign and resign. To re-sign a contract is to sign it again. To resign is to quit. One hyphen, and the two verbs have nothing to do with each other.
Co-op and coop. A co-op is a cooperative. A coop is where you keep chickens.
Frequently Asked Questions
When do I hyphenate a compound modifier?
Hyphenate it before the noun and leave it open after: "a well-known author" but "the author is well known." Adverbs ending in -ly are the main exception, since they never take a hyphen, even before a noun.
What is a suspended hyphen?
It is a hyphen left hanging when two compounds share a final word, as in "two- and three-day trips." Keep the space after the hyphen. The construction applies to numbers too: "a 5- and 10-year plan."
Is it "email" or "e-mail"?
Both are in use, but "email" has become the default at most American publishers and at most British ones as well. "E-mail" survives mainly in older style guides and in documents that have not been updated. Choose one and apply it without exception in a given document.
Do adverbs ending in -ly ever take a hyphen?
No. "A highly effective method" and "a carefully worded email" are correct without one. The rule covers only -ly adverbs, so "well-known," "fast-acting," and "long-running" all keep their hyphens.
How do I hyphenate numbers used as modifiers?
Hyphenate the entire unit when it modifies a noun: "a 30-year mortgage," "a 6-foot ladder." Drop the hyphens when the measurement stands alone: "the mortgage runs 30 years." Whether you write 30 or thirty depends on your style guide, not on the hyphen.
What is the difference between a hyphen and a dash?
A hyphen joins two words into one unit and takes no surrounding spaces. A dash separates parts of a sentence, and both the en dash and the em dash are longer marks with different jobs.
Decide once, then search
Pick the ten compounds you type most often, write the correct version of each in a style sheet, and run a find and replace over every draft before you publish. Hyphens are too small to police by eye and too meaningful to leave to chance.