If you ever wish to extend a work meeting, ask one of two questions: How many spaces belong after a period? or What is the difference between an “em” dash and an “en” dash? Either is guaranteed to prolong the discussion by at least 30 minutes. Neither will result in a productive use of anyone’s time.
Personally, I feel that the distinction between the “em” dash, and the “en” dash is the pickiest, most useless, and most irritating of all the distinctions that editors continue to maintain. However, I cannot deny that editors using the Associated Press Stylebook, the Publication Manual of the American Psychological Association, the Council of Science Editor’s Scientific Style & Format, or the Government Printing Office Style Manual, among many others, continue to maintain the distinction, and it does my poor writers no good for me to rail against the practice when they still have to struggle with it. So, for today, I will swallow my ire and explain the distinctions as best I can.
Writers should first be aware that the distinction between the “em” dash, and the “en” dash is a matter of style, not grammar. (In this case, we are working with a subset of grammar, orthography, the study of spelling and punctuation.) This article is intended to provide a broad overview of the two punctuation marks. As you are already aware, style guides differ, so check yours for specific guidance. Government writers should consult the GPO 8.60–8.75.
The names “en” and “em” dash are derived from typesetters’ descriptions of the font sizes. Today, these are variable according to the word processing program and the computer language the writer is using, so the terms are historical rather than descriptive.
As a matter of style, some uses, particularly of the “em” dash, are relegated to creative rather than technical writing. For example, creative writers may choose to use the “em” dash to indicate interruptions in dialogue, by others or by oneself, as in the case of stream-of-consciousness writing.
Creative writers may also use consecutive “em” dashes to omit letters, as in “Count D– — returned that night by coach to F– — Hall.” Editors of ancient or medieval manuscripts can use consecutive “em” dashes to indicate missing words, such as when lacunae appear in a damaged manuscript. The purpose of this article is not to delineate all uses of the marks of punctuation, but to identify such uses as are common to writers of scientific and technical publications.
How to Use the “En” Dash
Create the “En” Dash on a PC: En Dash = Ctrl + Num –
Create the “En” Dash on a MAC: option/alt + hyphen/minus sign
- “En” dashes connect ranges, such as Monday–Friday or 1950–65. In this case, it substitutes for words such as “to,” “from,” or “between,” so omit those words when using it.
- The “en” dash indicates direction, such as north–south or LA–Phoenix.
- The “en” dash suggests contests, substituting for the words “to,” “for,” “against,” or “versus,” as in USWNT won 10–0 over Puerto Rico or US–Iraq war.
- The “en” dash helps to join compound adjectives when one part of the phrase is not hyphenated, as in Post–World War II or ex–prime minister. Note that this is the most controversial use of the “en” dash. The words it connects go by different names, such as adjectival phrases, open compounds, phrasal compounds, or double compounds. Even when using the same style guide, editors will argue bitterly over how to place and space this dash. Remember to strive for internal consistency within a document.
How to Use the “Em” Dash
Create the “Em” Dash on a PC: Em Dash = Ctrl + Alt + Num –
Create the “Em” Dash on a MAC: option/alt + shift + hyphen/minus sign
- When greater or special emphasis is desired, use the “em” dash to substitute for:
Commas. The most significant of our findings—breeding disparity, food scarcity, and size difference—were all contingent upon stable geothermal patterns during the study period.
Parentheses. After uncovering the offender’s parking violations—134 in all—the prosecutor decided to seek the maximum sentence.
Colons. We examined three species of beach mice—Alabama, Florida, and Southeastern.
- The “em” dash can introduce a list.
That we submit them for review and corrections;
That we then accept them as corrected;
and That we also publish them.
- The “em” dash can replace bullet points.
This park is excellent for:
- Consecutive “em” dashes can indicate repetition in a works cited list.
Brown, Peter. “Ornithology.” Cornell Lab Home Page.
— —. “The Brown Pelican.” The Auk.
NOTE: Neither the “en” dash nor the “em” dash may be used with a space. The one exception is when using “em” dashes consecutively, as in to indicate repetition in a works cited list. Then a space is permitted between consecutive “em” dashes.
Chicago Manual of Style Q&A. “Hyphens, En Dashes, and Em Dashes.”
The Punctuation Guide. “Hyphens and Dashes.”
Stack Exchange. “English Language and Usage.”