Hyphenation Rules: When to Use Hyphens

Reviewed by the Grammarlyzer Editorial Team · Our Review Standards · Published January 22, 2026 · Updated June 13, 2026

Clean, consistent hyphens for professional writing.

Quick Answer

Use hyphens in compound adjectives before a noun (a well-known brand) and in compound numbers (twenty-one).

Skip hyphens after -ly adverbs (highly skilled writer).

Memory Trick: If two words act as one adjective, hyphenate them.

🔑 Key Takeaway

Hyphens clarify meaning and prevent misreading in compound modifiers.

When to Hyphenate

Hyphens mostly exist to prevent confusion. The big rule: hyphenate a compound modifier when it comes before the noun it describes, but usually not after.

Situation Rule Example
Compound adjective before a noun hyphenate a well-known author, a 10-year plan
Same words after the noun no hyphen The author is well known.
After an -ly adverb no hyphen a highly skilled team
Compound numbers 21–99 hyphenate twenty-one, fifty-six
Prefixes (most) usually closed; hyphen to avoid confusion preexisting, but re-sign vs resign

Common Mistakes

❌ Incorrect:

We offer a well designed dashboard.

✓ Correct:

We offer a well-designed dashboard.

"Well-designed" is a compound adjective before the noun "dashboard," so it takes a hyphen. After the noun it would drop it: "The dashboard is well designed."
❌ Incorrect:

a highly-rated restaurant

✓ Correct:

a highly rated restaurant

Never hyphenate after an -ly adverb. "Highly" already clearly modifies "rated," so the hyphen is redundant.
❌ Incorrect:

a small business owner (meaning the owner of a small business)

✓ Correct:

a small-business owner

Without the hyphen this reads as a small person who owns a business. The hyphen groups "small business" as one idea modifying "owner." This is where hyphens prevent real ambiguity.
❌ Incorrect:

I need to resign the contract (meaning sign again).

✓ Correct:

I need to re-sign the contract.

"Resign" means to quit; "re-sign" means to sign again. The hyphen after a prefix is needed whenever omitting it creates a different, real word.

🎯 Test Your Knowledge

1. "a five-year-old child" — before the noun, this needs a ___.

2. "The child is five years old." → ___

3. "a fully funded project" → ___ (after -ly adverb)

4. "thirty-two" (the number) → ___

5. "a state-of-the-art lab" (before the noun) → ___

See It Live: Check a Sentence With Our Engine

Below is the same Harper engine that powers the homepage editor, running right on this page—no upload, no server round-trip. The starter sentence is missing a hyphen in a compound modifier—fix it, or paste your own.

The correct version is: They signed a long-term lease for the office. "Long-term" is a compound adjective before "lease," so it takes a hyphen.

Honest limits: the engine reliably flags the mechanics—spelling, agreement, punctuation—but whether a sentence is clear is a judgment call. Use the hyphenation rules guidance above to decide if the structure actually serves the reader.

Frequently Asked Questions

Do you hyphenate a compound modifier when it comes after the noun?

No. Hyphenate the compound only before the noun: 'a well-known author.' When it follows the noun, drop the hyphen: 'the author is well known.'

Why is 'highly skilled writer' not hyphenated?

Adverbs ending in -ly already signal that they modify the next word, so the hyphen is redundant. The rule applies to all -ly adverbs: 'highly skilled,' 'newly elected,' 'poorly written.'

What is the difference between a hyphen, an en dash, and an em dash?

A hyphen (-) joins words like 'well-known.' An en dash (–) shows ranges like '1990–1995.' An em dash (—) sets off a break in a sentence. They look similar but do different jobs.

Word Origins & Etymology

Hyphen comes from Greek 'huphen' (together, under one), from 'hupo' (under) + 'hen' (one). The mark was originally placed under two words to show they should be read as one unit.

Hyphens join compound modifiers before a noun (well-known author), create compound numbers (twenty-one), and attach prefixes (self-taught, re-enter). They are NOT dashes.

🔗 The Connection

Hyphens (-) join words. En dashes (–) show ranges. Em dashes (—) create breaks. These three marks are visually similar but serve completely different functions.

Real-World Examples

📏 Compound Modifier:

She is a well-known author.

Hyphenate compound modifiers BEFORE the noun
📏 After Noun:

The author is well known.

No hyphen when the modifier comes AFTER the noun
📏 Numbers:

She has twenty-one years of experience.

Hyphenate compound numbers from twenty-one to ninety-nine
📏 Prefix:

He is a self-taught programmer.

Hyphenate with self-, all-, ex- (ex-president)
⚠️ Ambiguity:

Re-cover the sofa (cover again) vs recover from illness (get better).

Hyphens prevent confusion between different words
❌ Unnecessary:

She is a well-known teacher who is well-known in the community.

Second instance wrong: no hyphen after the noun. 'who is well known'

Why Do People Confuse Them?

Hyphenation rules are among the most inconsistent in English because compound words evolve through three stages: open (ice cream), hyphenated (ice-cream), and closed (icecream → not standard yet, but email started as e-mail). Different style guides disagree on specific compounds, making 'correct' hyphenation a moving target.

For more practice, see Semicolon Usage and Comma Rules.

Related Articles

Hyphenation When Accuracy Changes Meaning

In business writing, hyphenation decisions affect clarity, professional appearance, and brand consistency. Style guides maintained by publishing houses, corporations, and news organizations typically include explicit hyphenation lists for frequently used compound adjectives in their domain — terms like "decision-making process," "industry-leading solutions," "full-time employee," and "client-facing team." Writers who ignore these conventions create inconsistency within and across documents. A product description that uses "state of the art technology" on one page and "state-of-the-art technology" on another signals poor editorial control. When in doubt in a business context, hyphenate the compound modifier if it appears before the noun and remove the hyphen if it follows the noun ("a well-known author" vs. "the author is well known").

In academic writing, hyphenation intersects with clarity in technical terminology, compound adjectives in research descriptions, and the presentation of discipline-specific concepts. The American Psychological Association, Chicago Manual of Style, and MLA each provide hyphenation guidance, and they do not always agree. APA, for instance, has detailed tables for hyphenating compounds formed with prefixes (non-, pre-, post-, re-), while Chicago's approach differs in several cases. Graduate students submitting manuscripts to journals must match the hyphenation style of the target publication, and inconsistency in this area can invite requests for revisions. Prefixed words like "non-native," "pre-existing," and "self-report" are particularly variable across style guides.

The most common hyphenation errors cluster around four situations. First, writers omit hyphens in compound modifiers before nouns, producing ambiguities like "small business owner" (is the owner small, or is it a small business?). Second, they add hyphens after adverbs ending in "-ly," writing "quickly-written report" instead of "quickly written report" — the "-ly" suffix already signals modification, making the hyphen redundant. Third, they hyphenate established open compounds that dictionaries list as two words ("health care," "real estate"). Fourth, they fail to apply hyphens consistently to number-noun compounds ("five-year plan," "two-week notice") when these appear before the modified noun.

The Before-Noun Test for Compound Modifiers

When two or more words function together as a single modifier before a noun, hyphenate them: "a long-term strategy," "a well-designed system." When the modifier follows the noun (especially after a linking verb), omit the hyphen: "the strategy is long term," "the system is well designed." Never hyphenate compound modifiers that include an adverb ending in -ly, regardless of position.

Plain-English Questions About Hyphenation Rules

Do I need to hyphenate words with prefixes like "non-" and "pre-"?

It depends on the style guide. The Chicago Manual of Style generally recommends closing up prefix combinations without a hyphen ("nonstandard," "predetermined," "postwar") unless doing so creates a doubled vowel that looks awkward ("pre-eminent" vs. "preeminent") or results in confusion with another word. APA has more detailed prefix tables and recommends hyphens in some cases where Chicago does not. Merriam-Webster Dictionary is the default authority for Chicago and records current standard usage. When "non" precedes a proper noun or a compound word, a hyphen is required: "non-English-speaking" and "non-self-governing" need hyphens for clarity.

Why don't I hyphenate adverb-adjective compounds before nouns?

Adverbs ending in "-ly" are already grammatically marked as modifiers by that suffix, so adding a hyphen is redundant — readers can already identify the adverb and understand its relationship to the following adjective. "Quickly written report" is unambiguous because "quickly" can only modify "written," not "report." Contrast this with "fast-written report," where "fast" could theoretically be read as modifying "report" (a fast report), making the hyphen useful for disambiguation. The rule holds for all "-ly" adverbs: "highly recommended book," "poorly designed interface," "newly elected official" — none take a hyphen before the noun.

How do I know if a compound is one word, hyphenated, or two words?

The only reliable method is to look it up in a current dictionary. Many compounds move from two words to hyphenated to one word as they become more established in the language: "on-line" became "online," "e-mail" is becoming "email," "data base" became "database." Your dictionary entry will tell you the current standard form. For new technical or industry-specific compounds not yet in dictionaries, your style guide's general rules apply. When the compound functions as a noun, use the dictionary form. When it functions as an adjective before a noun, apply the compound-modifier hyphenation rule regardless of the dictionary form of the noun version.

Should numbers and fractions always be hyphenated?

Fractions used as modifiers before nouns are hyphenated: "a two-thirds majority," "a one-half share." When used as nouns, some style guides prefer no hyphen: "two thirds of the vote." Compound number adjectives before nouns follow the standard compound-modifier rule: "a five-year plan," "a 10-page report," "a three-month delay." Spelled-out numbers from twenty-one to ninety-nine are hyphenated when written out: "forty-seven," "thirty-two." Numbers over one hundred are not hyphenated: "two hundred," "three thousand." These rules are fairly stable across major style guides, though Chicago and AP Stylebook differ on when numbers should be spelled out versus written as numerals.

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