A dash is a little horizontal line that floats in the middle of a line of text (not at the bottom; that’s an underscore). It’s longer than a hyphen and is commonly used to indicate a range or a pause. Dashes are used to separate groups of words, not to separate parts of words like a hyphen does. (Learn more about the difference between a dash and a hyphen here). There are three kinds of dashes: the em dash, the en dash, and the double hyphen.
The most common types of dashes are the en dash (–) and the em dash (—). A good way to remember the difference between these two dashes is to visualize the en dash as the width of the letter N and the em dash as the width of the letter M. These dashes not only differ in length, however, they also serve different functions within a sentence.
What are em dashes?
Em dashes save the day when other punctuation would be awkward. For instance, a single em dash can replace a pair of parentheses around material at the end of a sentence, or a pair of em dashes can replace a pair of commas around a clause that contains other commas, to make the sentence easier to understand.
Colons enable a writer to introduce a clause that amplifies whatever came before the colon. They are more formal than em dashes. However, em dashes are more emphatic than colons. When you want to generate strong emotion in your writing or create a more casual tone, use em dashes. Compare these sentences:
Writers and transcriptionists often replace unknown or intentionally omitted letters with em dashes. In these cases, em dashes appear two or three in a row.
What are en dashes?
Recall that en dashes are slightly narrower in width than em dashes. En dashes may look similar to em dashes, but they function in a much different way.
En dash indicating spans or ranges
The en dash is often used to indicate a span of time or a range of numbers. In this context, the dash should be interpreted as meaning either “to” or “through.” Consider the examples below:
En dash indicating a connection
The en dash may also be used to indicate a connection between two words. You can use an en dash in a complex compound adjective when one or both of its elements are already hyphenated compounds, although it’s also acceptable to use hyphens in these kinds of constructions—just be consistent.
When one element of a complex compound adjective is a proper noun made up of two or more words, however, the proper noun is left open and connected to the rest of the phrase with an en dash:
