Were you taught to put two spaces after a period at the end of a sentence? Many people were, but now most publications recommend using just one. Here's the scoop.
The Shift to One Space After a Period
But the story of spaces at the end of sentences may be more complicated than the traditional lore because in the years of professional printing before the typewriter, typesetters tended to use wide spaces at the end of sentences whether their fonts were monospaced or proportional. Yet, it is true that during the era of the typewriter, two spaces ruled, and once computers became the dominant tool for typing, one space became the standard.
In HTML and many blogging platforms, no matter how many spaces you type, they get turned into one space. If you want multiple spaces, you have to hard code it in using the HTML code for a space, such as which gives you a nonbreaking space. That means the program won’t break a line at the space—it’s a way to keep two words together so they don’t end up on two lines, such as a date or a name—but using the “nbsp” code is also a way to force HTML to include more than one space.
See Also: How Many Spaces After A Period?
Types of Spaces
You may also be surprised to learn that professional typesetters use different kinds of spaces. I first learned about these when I heard about something called a thin space—what typesetters often use between a single quotation mark and a double quotation mark that have to go next to each other. A full space between them would look weird, but if you put nothing between them, they run together, so typesetters use an extra narrow thin space to give the two punctuation marks a slight separation.
Typesetters use the various spaces available to them to do things such as align tables, set mathematical formulas, and properly align poetry.
[Correction: This article original said that the APA style manual called for one space, but this information was based on the previous edition of the manual. They changed their style from one space after a period to two spaces for manuscripts in the new, sixth edition.]
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