What is the difference between a hyphen and a dash?
A hyphen (-) is the shortest mark and is used to join words together (well-known, self-esteem, twenty-three). An em dash (--) is the longest mark and is used to set off parenthetical information, create dramatic pauses, or replace commas, parentheses, or colons in certain contexts.
Hyphens, em dashes, and en dashes may look like variations of the same mark, but they serve entirely different functions in English writing. Confusing them is one of the most common typographical errors in professional documents, and it is easy to see why: on most keyboards, only the hyphen has a dedicated key, while the em dash and en dash require special key combinations or autocorrect features.
This guide gives you a complete, practical breakdown of all three marks. You will learn exactly when to use each one, how to type them on any device, what the major style guides say, and how to avoid the mistakes that mark amateur writing. Whether you are drafting a business report, a marketing brochure, a novel, or an academic paper, these rules will sharpen your punctuation immediately.
The Three Marks at a Glance
| Mark | Name | Length | Symbol | Primary Use |
|---|---|---|---|---|
| - | Hyphen | Short | - | Joining words (compound modifiers, prefixes) |
| -- | Em dash | Long | --- | Parenthetical breaks, emphasis, interruptions |
| (medium) | En dash | Medium | -- | Ranges, compound adjectives with multi-word elements |
"These three marks are not interchangeable. A hyphen joins, an em dash interrupts, and an en dash spans. Using the wrong one is a typographical error, not a style choice." -- The Chicago Manual of Style, 17th edition [1]
The Hyphen (-)
The hyphen is the shortest of the three marks. Its primary job is to join words or parts of words together.
Rule 1: Compound Modifiers Before a Noun
When two or more words work together as a single adjective before a noun, join them with a hyphen:
- a well-known author
- a high-quality product
- a full-time position
- a state-of-the-art facility
- a decision-making process
When the same modifiers come after the noun, the hyphen is usually dropped:
- The author is well known.
- The product is high quality.
Exception: Some compound modifiers are always hyphenated regardless of position (check a dictionary when in doubt).
Rule 2: Prefixes
Hyphens connect certain prefixes to root words. The rules vary by style guide, but the most common cases are:
| Prefix Situation | Hyphen? | Example |
|---|---|---|
| Prefix before a proper noun or number | Yes | pre-World War II, mid-2020s |
| Prefix creates a double vowel | Sometimes | re-enter, co-opt (but cooperate is also accepted) |
| Prefix self- | Always | self-esteem, self-directed |
| Prefix ex- (meaning former) | Always | ex-president, ex-employee |
| Prefix all- | Always | all-inclusive, all-purpose |
| Most other prefixes | Usually no | unprecedented, resubmit, coauthor |
Rule 3: Numbers and Fractions
Hyphenate compound numbers from twenty-one through ninety-nine, and written-out fractions used as adjectives:
- Twenty-three people attended.
- A two-thirds majority is required.
- The project is three-quarters complete.
Rule 4: Avoiding Ambiguity
Use a hyphen when removing it would create confusion:
- re-cover (cover again) vs. recover (get better)
- re-sign (sign again) vs. resign (quit)
- re-creation (creating again) vs. recreation (leisure)
Common Hyphenation Errors
Over-hyphenation: Do not hyphenate a compound modifier when the first word is an adverb ending in -ly:
- Wrong: a highly-effective strategy
- Right: a highly effective strategy
The -ly adverb already signals that it modifies the next word, so the hyphen is unnecessary.
"Never hyphenate a compound modifier that starts with an adverb ending in -ly. The -ly ending does the work the hyphen would do." -- AP Stylebook, 56th edition [2]
The Em Dash (--)
The em dash is the longest of the three marks (roughly the width of the letter M). It is the most versatile dash and the one most people think of when they say "dash." In plain text, it is commonly represented as two hyphens (--).
Rule 1: Parenthetical Statements
Use em dashes to set off a parenthetical element -- a phrase or clause that adds information but could be removed without changing the sentence's core meaning:
- The proposal -- which took three months to develop -- was approved unanimously.
- Our biggest client -- a Fortune 500 company -- renewed their contract.
- The data -- surprisingly -- supported the original hypothesis.
Em dashes are stronger than commas and more informal than parentheses. They draw the reader's eye to the inserted information.
Rule 2: Emphasis on a Concluding Element
An em dash can replace a colon when you want to add dramatic emphasis to the final part of a sentence:
- After months of negotiation, we finally got what we wanted -- full ownership.
- She had been preparing for this moment her entire career -- and she was ready.
Rule 3: An Abrupt Break or Change in Thought
- I was about to approve the budget -- but then I saw the revised numbers.
- The system was supposed to be ready by -- well, it was supposed to be ready last week.
Rule 4: Replacing Commas for Clarity
When a sentence already contains several commas, em dashes can set off a parenthetical element without adding to the comma clutter:
- The marketing team, sales department, and product group -- all of which had been consulted -- agreed on the new strategy.
Spacing Around Em Dashes
Style guides differ on whether to put spaces around em dashes:
| Style Guide | Spacing | Example |
|---|---|---|
| Chicago Manual of Style | No spaces | The team--all twelve members--agreed. |
| AP Stylebook | Spaces | The team -- all twelve members -- agreed. |
| Most book publishers | No spaces | The team--all twelve members--agreed. |
| Most newspapers | Spaces | The team -- all twelve members -- agreed. |
Choose one style and be consistent throughout your document.
How Many Em Dashes Per Paragraph?
Em dashes lose their impact when overused. A good guideline: no more than two em dashes per paragraph. If you find yourself reaching for a third, consider whether commas, parentheses, or sentence restructuring would serve you better.
The En Dash
The en dash is the middle-length mark (roughly the width of the letter N). It has two primary uses, both of which are distinct from the hyphen and the em dash.
Rule 1: Ranges
The en dash replaces the word "to" or "through" in ranges of numbers, dates, and times:
- Pages 45--67
- The 2020--2024 fiscal period
- Monday--Friday, 9:00 AM--5:00 PM
- Chapters 3--7
Important: Do not use an en dash with the words "from" or "between." These words require "to" and "and," respectively:
- Wrong: from 2020--2024
- Right: from 2020 to 2024
- Wrong: between 9:00--5:00
- Right: between 9:00 and 5:00
Rule 2: Compound Adjectives with Multi-Word Elements
When a compound adjective includes a multi-word element (a proper noun, a phrase, or an already-hyphenated term), use an en dash instead of a hyphen:
- the New York--based company (New York is two words)
- a Nobel Prize--winning scientist
- the post--World War II economy
- a public--private sector partnership
This usage is most commonly observed in formal publishing and academic writing. Many business writers use a hyphen in these cases, and most readers will not notice the difference. But for publications that follow Chicago Manual style, the en dash is the correct choice.
"The en dash is used in place of a hyphen in a compound adjective when one of the elements consists of two words or a hyphenated word." -- The Chicago Manual of Style, 17th edition [1]
AP Style Note
The AP Stylebook does not use the en dash. AP style substitutes a hyphen for all en dash uses. If you follow AP, you can disregard the en dash entirely and use hyphens for ranges and compound adjectives.
Summary Table: When to Use Each Mark
| Situation | Mark | Example |
|---|---|---|
| Compound modifier before a noun | Hyphen | a well-known fact |
| Prefix + proper noun | Hyphen | pre-World War II |
| Self- / ex- compounds | Hyphen | self-aware, ex-CEO |
| Written-out numbers (21-99) | Hyphen | forty-two |
| Parenthetical break in a sentence | Em dash | The plan -- our best option -- was approved. |
| Emphasis before final element | Em dash | She finally found it -- the missing file. |
| Abrupt change or interruption | Em dash | I thought we could -- wait, never mind. |
| Number/date/time ranges | En dash | 2020--2025, pages 1--15 |
| Compound adjective with multi-word element | En dash | a San Francisco--based startup |
How to Type Each Mark
On Windows
| Mark | Method |
|---|---|
| Hyphen | Press the hyphen key (-) |
| Em dash | Alt+0151 (numeric keypad) or Ctrl+Alt+Minus in Word |
| En dash | Alt+0150 (numeric keypad) or Ctrl+Minus in Word |
On Mac
| Mark | Method |
|---|---|
| Hyphen | Press the hyphen key (-) |
| Em dash | Option+Shift+Minus |
| En dash | Option+Minus |
In HTML
| Mark | Code |
|---|---|
| Hyphen | - (just the character) |
| Em dash | — or — |
| En dash | – or – |
In Plain Text and Markdown
When the typographic characters are not available, the standard convention is:
- Hyphen: a single hyphen (-)
- Em dash: two hyphens (--)
- En dash: context makes it clear (use a single hyphen for ranges in plain text)
Hyphens, Em Dashes, and En Dashes in Professional Contexts
Each mark appears in specific professional writing situations. Understanding these contexts helps you apply the rules confidently.
| Professional Context | Most Common Mark | Typical Usage |
|---|---|---|
| Business reports | Em dash | Setting off parenthetical data or clarifications within sentences |
| Legal contracts | En dash | Specifying date ranges, section ranges (Sections 4--7) |
| Marketing copy | Em dash | Creating dramatic emphasis before a key benefit or tagline |
| Academic papers | En dash, hyphen | En dashes for page ranges in citations; hyphens for compound modifiers |
| Technical documentation | Hyphen | Compound modifiers in specifications (32-bit processor, user-defined settings) |
| Journalism | Em dash (with spaces) | Parenthetical insertions and attribution in quotes |
| Resumes and CVs | En dash | Date ranges for employment and education (2018--2022) |
Style Guide Comparison: Key Differences
The choice of mark sometimes depends on which style guide your organization follows. Here are the most significant differences:
| Situation | Chicago Manual of Style | AP Stylebook |
|---|---|---|
| Parenthetical break | Em dash, no spaces | Em dash, with spaces |
| Number ranges | En dash | Hyphen |
| Compound adjective with multi-word element | En dash | Hyphen |
| Score or vote (5--3) | En dash | Hyphen |
"In professional publishing, the difference between a hyphen and an en dash in a citation is the difference between a polished manuscript and a sloppy one. These details may seem trivial, but they are the signals that editors look for when assessing the quality of a submission." -- Amy Einsohn, The Copyeditor's Handbook, 4th edition [3]
Common Mistakes
Mistake 1: Using a Hyphen Where an Em Dash Is Needed
Wrong: The results - which surprised everyone - were published Friday. Right: The results -- which surprised everyone -- were published Friday.
A parenthetical break requires an em dash, not a hyphen.
Mistake 2: Using an Em Dash for a Range
Wrong: Pages 10--25 (using an em dash for a range) Right: Pages 10-25 (en dash for a range)
Ranges use the en dash, not the em dash.
Mistake 3: Hyphenating Adverb + Adjective Compounds
Wrong: a newly-hired employee Right: a newly hired employee
Adverbs ending in -ly do not take a hyphen when modifying an adjective.
Mistake 4: Inconsistent Spacing Around Em Dashes
Inconsistent: The proposal--which was late -- needed revisions. Consistent: The proposal -- which was late -- needed revisions.
Pick one spacing style and apply it throughout the document.
Related Punctuation Guides
- Comma Rules - Complete Guide -- commas and their many uses
- Semicolon Usage -- semicolons in detail
- Colon vs Semicolon -- comparing two misused marks
- The Oxford Comma -- the serial comma debate
- Apostrophe Rules -- possessives and contractions
Quick Decision Flowchart
When you are unsure which mark to use, follow this decision process:
Step 1: Are you joining two words to form a compound modifier or prefix?
- Yes: Use a hyphen (well-known, self-directed, pre-2020).
Step 2: Are you indicating a range of numbers, dates, or times?
- Yes: Use an en dash (pages 15--30, 2020--2024, Monday--Friday). In AP style, use a hyphen instead.
Step 3: Are you inserting a parenthetical break, creating emphasis, or showing an interruption?
- Yes: Use an em dash (The results -- surprisingly -- were positive).
Step 4: Are you connecting a multi-word element in a compound adjective?
- Yes: Use an en dash (a New York--based company, a post--Cold War policy). In AP style, use a hyphen.
If none of these apply, you probably do not need a dash or hyphen at all.
Frequently Mismarked Terms
These terms are commonly written with the wrong mark or no mark at all:
| Term | Correct Mark | Example |
|---|---|---|
| Long-term (before a noun) | Hyphen | a long-term investment |
| Long term (after a noun) | No mark | The investment is long term. |
| Part-time (before a noun) | Hyphen | a part-time employee |
| Year-over-year | Hyphens | year-over-year growth |
| Monday--Friday | En dash (or hyphen in AP) | Open Monday--Friday |
| 2020--2024 | En dash (or hyphen in AP) | The 2020--2024 strategic plan |
| Cost-effective | Hyphen | a cost-effective solution |
| State-of-the-art | Hyphens | a state-of-the-art facility |
Summary
Hyphens, em dashes, and en dashes are three distinct marks with three distinct functions. Hyphens join compound words and modifiers. Em dashes create parenthetical breaks, emphasis, and interruptions. En dashes mark ranges and connect multi-word elements in compound adjectives. Using the right mark in the right context is a hallmark of polished, professional writing. Learn the three rules, practice the keyboard shortcuts for your platform, and your documents will immediately look and read more professionally.
References
[1] The Chicago Manual of Style. 17th ed., University of Chicago Press, 2017.
[2] The Associated Press Stylebook. 56th ed., Associated Press, 2022.
[3] Einsohn, Amy. The Copyeditor's Handbook: A Guide for Book Publishing and Corporate Communications. 4th ed., University of California Press, 2019.
Frequently Asked Questions
What is the difference between a hyphen and a dash?
A hyphen (-) is the shortest mark and is used to join words together (well-known, self-esteem, twenty-three). An em dash (--) is the longest mark and is used to set off parenthetical information, create dramatic pauses, or replace commas, parentheses, or colons in certain contexts. An en dash (a mark slightly longer than a hyphen) is used for ranges (pages 10-25, 2020-2024) and compound adjectives involving multi-word elements (New York-based company). The three marks look similar but serve entirely different purposes.
When should I use an em dash in writing?
Use an em dash to insert a sudden break or parenthetical statement into a sentence, to set off an appositive that contains commas, or to emphasize a concluding element. For example: 'The proposal -- which took three months to develop -- was approved unanimously.' Em dashes add emphasis and visual impact that commas and parentheses do not. Most style guides recommend using them sparingly; overuse can make writing feel choppy or breathless. In formal academic writing, em dashes are less common than in journalism and creative writing.
How do I type an em dash and en dash?
On Windows, type an em dash with Alt+0151 on the numeric keypad, or use Ctrl+Alt+Minus on the numeric keypad in Microsoft Word. For an en dash, use Alt+0150 or Ctrl+Minus in Word. On Mac, type an em dash with Option+Shift+Minus and an en dash with Option+Minus. In many writing applications, typing two hyphens (--) will automatically convert to an em dash. In HTML, use — for em dash and – for en dash. Many professional writers simply type two hyphens and let their software handle the conversion.