Dash and Hyphen
A B2 guide to three marks that look similar but do different jobs — the hyphen for joining words and compound modifiers, the en dash for ranges, and the em dash for parenthetical breaks and emphasis.
Three Different Lines
English has three horizontal punctuation marks that look similar but have different jobs and different lengths:
| Mark | Length | Symbol | Main use |
|---|---|---|---|
| Hyphen | shortest | - | joins words and parts of words |
| En dash | medium | – | shows a range or a connection |
| Em dash | longest | — | sets off a strong break in a sentence |
Most people confuse them. Once you see the difference, the rules become clear.
The Hyphen (-)
The hyphen is the shortest of the three. Use it to join things.
Use 1: Compound Modifiers Before a Noun
When two or more words act together as a single adjective before a noun, hyphenate them.
a well-known author
a five-year-old child
a high-quality product
a state-of-the-art facility
a long-term plan
If the same modifier comes after the noun, no hyphen is needed.
| Before noun (hyphenate) | After noun (no hyphen) |
|---|---|
a well-known author | The author is well known. |
a five-year-old child | The child is five years old. |
up-to-date software | The software is up to date. |
Exception: do not hyphenate adverbs ending in
-ly.a quickly written report, nota quickly-written report.
Use 2: Compound Numbers and Fractions
twenty-one
thirty-five
one hundred and forty-seven
two-thirds of the class
a three-quarter turn
Use 3: Prefixes (Sometimes)
Most prefixes attach without a hyphen: unhappy, restart, prewar, cooperate.
Use a hyphen with a prefix when:
| Reason | Example |
|---|---|
| The prefix attaches to a proper noun | pre-Christmas, anti-American |
| Two of the same vowel collide | re-elect, co-owner |
| Avoiding confusion with another word | re-cover (cover again) vs. recover (get well) |
With self-, ex-, all- | self-aware, ex-husband, all-inclusive |
Use 4: Word Breaks at the End of a Line
In printed text, a hyphen can split a word at a syllable break when it falls at the end of a line. Most digital text avoids this.
The En Dash (–)
The en dash is the width of the letter n. It is longer than a hyphen and shorter than an em dash.
Use 1: Ranges
The en dash means “to” or “through” between two numbers, dates, or places.
pages 12–24
the 2010–2019 period
Monday–Friday, 9 a.m.–5 p.m.
the New York–London flight
the score was 3–2
Tip: in informal writing or when an en dash is unavailable, a hyphen (
-) is acceptable:pages 12-24.
Use 2: Connections Between Equal Things
a parent–child relationship
the cost–benefit analysis
a student–teacher conference
This use is common in academic writing and signals that the two terms are linked but separate.
The Em Dash (—)
The em dash is the width of the letter m. It is the most flexible mark in English — and the most overused.
Use 1: A Strong Break in a Sentence
An em dash can replace a comma, a semicolon, a colon, or parentheses to add a sudden break, an aside, or an emphasis.
I finally found the keys — in the freezer. (replaces a colon)
The dog — a fluffy golden retriever — wagged its tail. (replaces commas or parentheses)
I was about to leave — but then the phone rang. (replaces a semicolon)
Use 2: Parenthetical Insertions With Emphasis
Use a pair of em dashes around extra information you want to highlight more strongly than commas would.
The new policy — which the staff hated — went into effect on Monday.
Compare:
| Mark | Effect |
|---|---|
(parentheses) | quietest aside — feels like a whisper |
, commas , | normal pause |
— em dashes — | loudest, most emphatic |
Use 3: An Interruption or a Trail-Off
"I was going to say —" she stopped mid-sentence.
"You're not — you can't be serious."
Spacing
Style guides differ on whether to put spaces around an em dash.
| Style | Example |
|---|---|
| US (Chicago, AP) — no spaces | I waited—then I left. |
| UK / many web styles — spaces | I waited — then I left. |
Pick one and use it consistently.
Common Mistakes
| Mistake | Fix | Why |
|---|---|---|
a quickly-written report | a quickly written report | Don’t hyphenate adverbs ending in -ly. |
The author is well-known. | The author is well known. | Compound adjectives only take a hyphen before the noun. |
pages 12-24 (in formal writing) | pages 12–24 | A range takes an en dash, not a hyphen, in careful writing. |
She is a five year old child. | She is a five-year-old child. | Compound modifier before a noun → hyphenate. |
My ex husband called. | My ex-husband called. | Hyphenate ex- with a noun. |
She was tired -- she went home. | She was tired — she went home. | Two hyphens (--) is a typewriter shortcut for an em dash. In real text, use —. |
At-a-Glance Comparison
| Need | Use | Example |
|---|---|---|
| Join two-word adjective before noun | hyphen - | a long-term plan |
| Compound number 21–99 | hyphen - | forty-two |
| Prefix on a proper noun | hyphen - | pre-Christmas |
| Range “to / through” | en dash – | 2010–2019, 9 a.m.–5 p.m. |
| Connection between equals | en dash – | parent–child bond |
| Strong sentence break | em dash — | I left — without a word. |
| Paired emphasis | em dash — | The plan — bold and risky — failed. |
| Interrupted speech | em dash — | "I just —" he stopped. |
Practice: Exercises
Which sentence is correctly hyphenated?
Summary
The hyphen (-) joins: compound modifiers before a noun (well-known author), compound numbers (twenty-one), and certain prefixes (ex-husband, pre-Christmas).
The en dash (–) shows ranges (2010–2019, pages 12–24) and connections between equals (parent–child relationship).
The em dash (—) marks a strong break, an aside, or an interruption — and is the most flexible (and most overused) mark in English. Use a pair of em dashes around parenthetical material you want to emphasize.
The big rule: hyphenate compound modifiers before the noun, but not after. And remember -ly adverbs never take a hyphen.