Proper usage of periods: One space or two?

As a dinosaur who wrote the first chapters of her Ph.D. dissertation on a manual typewriter, I grew up leaving two spaces after every period. But times have changed, and today I leave only one space between a period and the new sentence that follows it.

The two spaces made sense when we used typewriters with monospacing, as Grammar Girl explains in “How many spaces after a period?” But now that we’ve switched to proportional fonts, one space has become the standard.

If you feel passionately that we should use two spaces, you’ve got company, as you’ll see in “How Many Spaces After a Period: One or Two?“

More posts about punctuation:
* How to punctuate bullet-pointed lists
* Bloggers’ top two punctuation mistakes

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