Hyphens and dashes can be confusing. What are they, exactly, and when should each be used?
The shortest of the bunch, hyphens are used within words and phrases; for example, the punctuation marks used in “thought-provoking” (a compound adjective), “mother-in-law” (a compound word), and “ice-skate” (a compound verb) are hyphens. They’re also used to connect prefixes and suffixes to other words, such as pre-, post-, co-, re-, and so on, and can be vital in preserving clarity of meaning (compare “recover” with “re-cover”). Occasionally, they “hang” after words within a flowing sentence (“I love both nineteenth- and twentieth-century literature”).
Em dashes (—)
The em dash is a completely different animal. While a hyphen is used within words, em dashes are used within—and between—sentences. They are primarily used to break up passages, indicate pauses within written speech, and to enclose clauses. For example, one may wish to use them when speaking—or, rather, writing—about punctuation. In this case, the em dash is playing the role of parentheses or commas by separating a remark or aside from the main sentence—but they can also be used to somewhat replace colons, as in this example. In this way, they can add emphasis, clarity, and smoothness to your writing. Em dashes can also be used to redact or censor information (“The defendant, Mrs. T—, was detained”), or to replace curse words (“No s—, Sherlock!”) while retaining a passage’s meaning.
En dashes (–)
If you were unaware that a ‘dash’ could even be one of two things, don’t fear! En dashes are less common and controversial than em dashes and hyphens. They’re primarily used to indicate ranges. Examples include spans of numbers, dates, or times (“He read chapters 3–8 in preparation for class”, “The 2010–2011 report is now ready”, “The garage is closed from 11 a.m.–12 p.m. for lunch”), scores (“Italy drew with France 0–0”), or situations that require a connection to be drawn (“She caught the Hong Kong–Singapore flight”).
A note on spacing and style
When using any of the above punctuation marks, no spaces should be included either before or after (except in the case of the hanging hyphen, which necessarily has a space afterwards). However, as noted on thepunctuationguide.com, “most newspapers — and all that follow AP style — insert a space before and after the em dash” (as written here). Additionally, some writers opt to simply use hyphens and dashes as they prefer, replacing hyphens with en dashes, and em dashes with en dashes.
While there are distinct “rules” for when and how to use each punctuation mark, it is ultimately a matter for your individual style guide. For more on this, see our blog posts on why you need a style guide, and how to create one.