Hyphenation Rules: When and How to Use Hyphens

What Is a Hyphen?

The hyphen (-) is the shortest of the three horizontal punctuation marks commonly confused with one another: the hyphen, the en dash, and the em dash. While dashes separate, the hyphen joins—it connects words or parts of words to form compound terms, clarify meaning, and prevent misreading.

Hyphenation is one of the trickiest areas of English punctuation because the rules are not always absolute. Whether a compound word takes a hyphen can depend on its position in a sentence, the specific words involved, the dictionary you consult, and even the style guide you follow. Compounds that start as hyphenated forms often evolve into closed compounds (single words) over time—"e-mail" became "email," "on-line" became "online."

Despite these complexities, there are clear and reliable guidelines that cover the vast majority of hyphenation decisions. This guide walks through all of them.

Compound Modifiers Before a Noun

The most important hyphenation rule: when two or more words work together as a single adjective before a noun, they should usually be hyphenated:

• a well-known author
• a high-quality product
• a long-term investment
• a full-time employee
• a three-bedroom apartment
• a 15-year-old student
• a state-of-the-art facility
• a once-in-a-lifetime opportunity

The purpose of the hyphen is to show the reader that these words function as a unit. Without the hyphen, ambiguity can arise. Consider "small business owner"—does this mean a small owner of a business, or an owner of a small business? "Small-business owner" makes the meaning clear.

Multi-Word Modifiers

Modifiers of three or more words are connected with hyphens throughout:

• an out-of-date manual
• a do-or-die situation
• a matter-of-fact tone
• a first-come-first-served basis

Compound Modifiers After a Noun

When the same compound modifier appears after the noun it describes, the hyphen is usually dropped because there is less risk of ambiguity:

• The author is well known.
• The product is high quality.
• The investment is long term.
• She works full time.

However, some compounds are always hyphenated regardless of position—particularly those listed as hyphenated in the dictionary:

• The machine is well-oiled. (always hyphenated per some dictionaries)
• The decision was ill-advised.

When in doubt, consult a dictionary. If the compound appears as a hyphenated entry, keep the hyphen in all positions.

Adverbs Ending in -ly

Do not hyphenate a compound modifier when the first word is an adverb ending in -ly:

• a beautifully written novel (not "beautifully-written")
• a highly effective strategy (not "highly-effective")
• a poorly designed website (not "poorly-designed")
• a widely recognized expert (not "widely-recognized")

The -ly ending already signals to the reader that the word is modifying the next word, so the hyphen is unnecessary. This rule applies only to -ly adverbs, not to adjectives that happen to end in -ly:

• a friendly-looking dog (correct—"friendly" here is an adjective, not an adverb)
• a lonely-sounding melody (correct)

Hyphens with Prefixes

Most prefixes are attached directly to the root word without a hyphen: unhappy, prehistoric, semicircle, nonfiction, rewrite. However, hyphens are needed in several specific situations:

Before Proper Nouns and Numbers

• pre-Victorian, post-World War II, anti-American, mid-2020s

With the Prefix "Self-"

"Self-" almost always takes a hyphen:

• self-aware, self-esteem, self-employed, self-discipline

With the Prefix "Ex-" (Meaning "Former")

• ex-president, ex-wife, ex-employee

To Avoid Doubled Vowels or Consonants

• anti-intellectual (not "antiintellectual")
• co-owner (not "coowner")
• re-enter (not "reenter"—though some dictionaries accept "reenter")

To Prevent Confusion with Another Word

• re-cover (cover again) vs. recover (get better)
• re-sign (sign again) vs. resign (quit)
• re-creation (creating again) vs. recreation (leisure activity)

Hyphens with Suffixes

Suffixes are less likely to require hyphens than prefixes, but some cases exist:

• Suffixes before proper nouns: Obama-like, Shakespeare-esque
• The suffix -elect: president-elect, governor-elect
• Avoiding triple letters: bell-like (not "belllike"), shell-less (not "shellless")

Numbers and Fractions

Hyphens are used in spelled-out compound numbers and fractions:

Compound Numbers

All compound numbers from twenty-one through ninety-nine are hyphenated:

• twenty-one, thirty-five, forty-eight, sixty-seven, ninety-nine

Fractions Used as Modifiers

Fractions are hyphenated when they modify a noun:

• a two-thirds majority
• a one-half share

Numbers in Compound Modifiers

• a 10-minute walk
• a 200-page report
• a 50-meter pool
• a five-star hotel

Compound Nouns

Compound nouns can be open (two words), hyphenated, or closed (one word). Unfortunately, there is no single rule that determines which form a compound noun takes—it depends on convention and usage:

The best approach for compound nouns is to consult a current dictionary. Compound nouns tend to evolve from open to hyphenated to closed over time as they become more familiar.

Suspended Hyphens

When two or more hyphenated compounds share a common element, you can use suspended hyphens to avoid repetition:

• full- and part-time employees (instead of "full-time and part-time employees")
• first-, second-, and third-place finishers
• pre- and post-war architecture
• 10- to 15-minute intervals

Note the space after the suspended hyphen: "full- and part-time," not "full-and part-time."

Avoiding Ambiguity

One of the hyphen's most valuable functions is preventing misreading:

When in doubt about whether to hyphenate, ask yourself: could this be misread? If yes, add the hyphen.

Ages, Colors, and Directions

Ages

Ages are hyphenated when used as compound modifiers or compound nouns:

• a five-year-old child (modifier before noun)
• The five-year-old started school. (noun)
• She is five years old. (predicate—no hyphens)

Colors

Hyphenate color compounds when they modify a noun and the colors blend:

• a blue-green sweater (one color that's a blend)
• a blue and green sweater (two separate colors)

Directions

Compound directions are hyphenated: north-south, east-west, northeast (closed), north-northeast (hyphenated).

The Evolving Nature of Hyphens

Hyphenation in English is not static. Compounds tend to follow a life cycle: they start as open compounds (two separate words), evolve into hyphenated compounds, and eventually become closed compounds (single words). Consider these historical progressions:

• e-mail → email
• on-line → online
• web site → web-site → website
• to-day → today
• base-ball → baseball

This evolution means that hyphenation rules you learned years ago may have changed. Always check a current dictionary when unsure, and be aware that British and American dictionaries sometimes disagree on hyphenation.

Summary and Key Takeaways

• Hyphenate compound modifiers before a noun: "well-known author."
• Usually drop the hyphen after the noun: "The author is well known."
• Never hyphenate after an -ly adverb: "a highly effective strategy."
• Use hyphens with prefixes before proper nouns, after "self-" and "ex-," and to avoid confusion.
• Hyphenate compound numbers (twenty-one) and fractions as modifiers (two-thirds majority).
• Use suspended hyphens to streamline lists: "full- and part-time."
• When in doubt, ask: could this be misread? If yes, add a hyphen.
• Consult a current dictionary—hyphenation conventions evolve over time.

For more on related topics, see our guides to em dashes, en dashes, and hyphens, capitalization rules, and all punctuation marks.