This article explains the difference between hyphens, en dashes and em dashes.
It is one of the little-known secrets of good writing that dashes come in different sizes. The table below compares a hyphen with en and em dashes and shows how to obtain them from within Microsoft Word. (Other programs might not support dashes.)
Keys within MS Word (PC)
minus or numeric-minus*
Ctrl + numeric-minus
Ctrl + Alt + numeric-minus
(* The numeric minus key is the minus key at the top-right corner of your keyboard’s numeric keypad.)
The en dash is the width of a letter n — about half-again the width of a hyphen. The em dash is the width of a letter m — about twice the width of a hyphen.
When to use hyphens
Hyphens are used within some names (e.g. Crichton-Browne), to separate some prefixes from a root word (e.g. pre-empt), and in compound adjectives (e.g. role-playing game).
When to use en dashes
The most common use of the en dash is to indicate a span. For example:
- See lines 24–29
- Open Monday–Friday
Another use of the en dash is to act as a minus sign. (A hyphen is too narrow.) For example:
- 10 – 3 = 7
Note: When used to indicate a span the en dash is generally not surrounded with spaces. When used as a minus sign it is.
When to use em dashes
The most common use of em dashes is instead of commas when setting off a parenthetical comment. For example:
- Item 12, the broken CPU, is to be repaired today.
- Item 12 — the broken CPU — is to be repaired today.
Note: Some editors surround em dashes with spaces, others do not. There is no clear convention, so you are free to choose whichever you prefer. Be consistent, though.