I am always amazed when I am working on formatting issues with my students and I mention to them that they should have just one space after a period, not two. Alas, the consternation! The heavy sighs, the panicked looks, the livid faces! Generally, someone will say, "But my other English teacher said we should have TWO spaces after a period."
I'm always tempted to say, "But is your other English teacher giving you a grade for this class?"
Instead, though, I work to smooth over ruffled feathers. You see, people really don't like change, and students like change least of all. And when you start messing with their spaces after punctuation, well, you have a potential mutiny on your hands. Yes, they're right. The rule USED to be two spaces after a colon, a period, and other closing punctuation marks. However, now it's one space.
Why only one space? The publishing industry is partly to blame. In publishing, space is money, and an extra space after each closing punctuation mark is wasted space--and therefore, wasted money.
Additionally, PCs have to take part of the blame. Remember the old Courier font? Well, each letter of the Courier font takes up the same amount of space--for example, an i and an m would each take up the same amount of space--so we needed two spaces after the period in order to be better able to recognize where one sentence stopped and the next began. Now, however, we have proportional-spacing fonts, which means that each letter takes up only the amount of space it needs--an i takes up less space than an m, and therefore one space after a period is sufficient.
Bill Walsh, copy chief at The Washington Post's National Desk, discusses the spacing issue in the first chapter of his book The Elephants of Style: A Trunkload of Tips on the Big Issues and Gray Areas of Contemporary American English:
Are you still putting two spaces after periods, exclamation points, question marks and colons? You shouldn't be. Some places are still clinging to this typewriter convention, no doubt, but as a standard operating procedure it went out with the IBM Selectric. (3)If you're a student, however, you're perhaps more interested in what your particular citation format handbook has to say. Here is a rundown of a few of the more commonly used citation styles:
APA Style, from the Publication Manual of the American Psychological Association, 15th ed. (2001), p. 290
5.11 Spacing and Punctuation
Space once after all punctuation as follows:
Exception: Do not space after internal periods in abbreviations (e.g., a.m., i.e., U.S.) or around colons in ratios.
- after commas, colons, and semicolons;
- after punctuation marks at the ends of sentences;
- after periods that separate parts of a reference citation; and
- after the periods of the initials in personal names (e.g., J. R. Zhang).
CMS Style, from The Chicago Manual of Style, 15th ed. (2003), p. 61
2.12 Line spacing and word spacing.
A single character space, not two spaces, should be left after periods at the ends of sentences (both in manuscript and in final, published form) and after colons.
Turabian Style, from A Manual for Writers of Research Papers, Theses, and Dissertations, 7th ed., p. 375
A.1.3 Spacing and Indentation
Put only one space, not two, following the terminal punctuation of a sentence.
MLA Style, from MLA Handbook for Writers of Research Papers, 6th ed. (2003), pp. 93-94
3.2.12 Spacing after Concluding Punctuation MarksI deal with MLA format last because although the other formats require one space after closing punctuation, MLA is a little, well, forgiving:
Publications in the United States today usually have the same spacing after a period, a question mark, or an exclamation point as between words on the same line. Since word processors make available the same fonts used by typesetters for printed works, many writers, influenced by the look of typeset publications, now leave only one space after a concluding punctuation mark. In addition, most publisher's guidelines for preparing a manuscript on disk ask professional authors to type only the spaces that are to appear in print. [. . . ] [I]nternal punctuation marks, such as a colon, a comma, and a semicolon, should always be followed by one space.
As a practical matter, however, there is nothing wrong with using two spaces after concluding punctuation marks unless an instructor requests that you do otherwise. (94)And I say, come now, MLA! What gives?
I suspect that the Modern Language Association is catering to the traditionalists who can't break the habit (or simply aren't willing to) of typing two spaces after a period; therefore, the MLA Handbook offers them a one-sentence license to forgo industry and academic standards. Is it any wonder my students complain that their other English teacher did things differently?
Bottom line: One space after closing punctuation. Period.