The humble period (or full stop) is the workhorse of the English language. While it seems simple—just a dot to end a sentence—it has a few specific rules that keep your writing professional and clear.
1. Ending Declarative Sentences
The primary job of a period is to mark the end of a complete thought that isn't a question or an exclamation.
Example: The cat sat on the mat.
Indirect Questions: Use a period for sentences that report a question rather than asking it directly.
Direct: Where is the coffee?
Indirect: I wonder where the coffee is**.**
2. Abbreviations
Periods are often used to indicate that a word has been shortened.
Titles: Mr., Mrs., Dr., Sr.
Time: 6:00 a.m., 500 B.C.
Latin Abbreviations: etc., e.g., i.e.
Pro Tip: In British English, periods are often omitted for titles that end with the same letter as the full word (e.g., Mr instead of Mr. and Dr instead of Dr.). In American English, the period is almost always included.
3. Punctuation with Quotations
This is where most people get tripped up. The placement depends entirely on which "flavor" of English you are using:
American English: The period always goes inside the quotation marks.
Example: She said, "I'll be there soon**.**"
British English: The period usually goes outside unless it is part of the original quoted speech.
Example: She said, "I'll be there soon".
4. The "One Space" Rule
In the era of typewriters, it was standard to put two spaces after a period. In the modern digital age, one space is the standard. Using two spaces can make your text look dated or create awkward gaps in digital layouts.
Common Pitfalls to Avoid
The Run-on: Don't use a comma where a period belongs (comma splice).
Wrong: I love pizza, it is delicious.
Right: I love pizza**.** It is delicious.
Double Trouble: If a sentence ends with an abbreviation that has its own period, do not add a second period.
Right: Please arrive by 8:00 a.m. (Not a.m..)