It’s often difficult to decide when to use a hyphen or dash, and whether to use a long (em) dash or a short (en) dash. The letters ‘m’ and ‘n’ are used to describe the length of the dash as the same as the matching letter.
- The em-dash (—) is often used to set apart a piece of text, and can replace commas, parentheses, or colons. The em-dash often comes in pairs—as in this sentence—to set off a thought. Note that correct usage has no space before or after the em-dash, though sometimes, it may appear in print that way. And the em-dash may sometimes be imitated by running two n-dashes or hyphens together (––, –)
- The en-dash (–) is often used to represent a range of numbers, dates, or times, and stands for “to” or “through”. For example, 1–10, 2014–2015, 9 am–5 pm. Note that there are no spaces on either side of the en-dash.
- The hyphen (-) is most often used to form terms made up of two or more words. Examples: She was a well-known politician. Check-out time is noon. It was a no-holds-barred contest.