The Basics

[1] To end a complete sentence

              See spot run.

[2] Abbreviations

              Mr., Mrs., Gov. Jenkins, Dist. Atty.

General Rule: use periods with abbreviations  that appear in lower case, but don't use periods with ones that appear in upper case.

              e
.g.     a.k.a.     etc.
              CEO   USA     NAACP     

Beyond the Basics

[3] To punctuate a fragment

              Sure.
              The car didn't slow. It stopped. Dead.

[4] A rhetorical question

              How many times do I have to tell you.
              What's the point.

Style note: Depending on the feel/tone of the rhetorical question, either a period or a question mark can be appropriate.

Syntax

No space before, one space after. (I know that some people still cling to the outdated style of using two spaces after a period, but thanks to modern kerning,
this is no longer necessary.)

With quotation marks: periods go inside the closing quote. (Unless your British, then all bets are off.)

              She said, "I see you
."

Don't use a period directly in front of a question mark.

Usage Key

Misuse

Don't use periods to punctuate a headline or subhead

Let's Talk Style

Let's see how the pros use it
Period (.)
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