How to Use a Period Correctly
There are two main categories of writing that determine how to use a period correctly within sentences; fiction writing and non-fiction writing.
This article is primarily about general English non-fiction writing, so please keep in mind that the rules for writing styles outside of this style may vary widely.
There are specific rules for writing where each period should be placed.
General Rule on How to Use a Period Correctly
These rules can vary slightly by writing style guide, but there is some general consensus among writing guides. This means that the end of every declarative or imperative sentence should have a period.
Declarative sentence:
“There are golf clubs in the car.”
Imperative sentence:
“Go and get me the golf clubs in the car.”
In both sentences the period is placed at the very end of the sentence.
Sentence Inside a Sentence
When a declarative sentence is quoted within another sentence by using quotation marks, use period only if the sentence ends with a quotation mark. Otherwise, use a comma to separate the two sentences.
She said without thinking, “Today is Tuesday.”
Here the second sentence ends with a quotation mark. Thus, we end it with a period.
“Today is Tuesday,” she said without thinking.
Here the quoted sentences is in the front of the compound sentence; it comes first. Therefore, we separate the two sentences with a comma and not with a period.
Abbreviations
Use a period when writing an abbreviation.
Exec. Mr. Mrs. Feb. i.e. e.g. Dr. St. Ave.
One Space
Use only one space when starting a new sentence after a period.
Avoid: “Today is Sunday. We’ll go to the zoo.”
Correct Way: “Today is Sunday. We’ll go to the zoo.”
Parenthesis and Period
If a sentence ends with a right parathesis, write the period after the right parenthesis.
American Civil War lasted four years (1861-1865).
But if a whole sentence is written inside a pair of paratheses, then the period should be placed BEFORE (inside) the right parathesis.
American Civil War lasted four years. (One of the bloodiest wars in which 600,000 people died.)
Decimal Point
In the United States, a period is used to separate a whole number from its decimals:
10.25 10,25 reads “ten and twenty-five hundredths”
99.467 reads “ninety nine and four hundred sixty seven thousandths”.
However, this is not the case in every country. In some parts of the world, a COMMA is used for what we in the U.S. know as “a decimal point.”
10,25 reads “ten and twenty-five hundredths”
1.225,90 reads “one thousand two hundred twenty-five and ninety hundredths”
IMPORTANT: If you are not aware the period convention of the region you are in, you can inadvertently make great errors when reading and using numbers.
Initials
Use periods after the initials in names.
Booker T. Washington
- Ravi Patel
If you have multiple initials in a name, do not include a space in between the initials:
Avoid: “J. R. Ewing”
Correct Way: “J.R. Ewing”
If the name is abbreviated into three letters, do not include a period in between capital letters.
Avoid: “F.D.R.”
Correct Way: “FDR”
Avoid: “C.I.A.”
Correct Way: “CIA”
Optional Periods When Writing Degrees and Titles
Periods are optional when writing degrees or titles.
BS or B.S.
RN or R.N.
PhD or Ph.D.
MBA or M.B.A.
Avoid Double Periods
If an abbreviation ends with a period, do not add a second period to mark the end of the sentence.
Avoid: “The train left at 8:30 a.m..”
Correct Way: “The train left at 8:30 a.m.”
Avoid: “The trains leave on time in E.U..”
Correct Way: “The trains leave on time in E.U.”
How to use a period correctly
Divide Run-On Sentences
Use period to divide run-on sentences into multiple independent sentences that read better.
Avoid: “She brought home poor grades her father grounded her for a week.”
Correct Way: “She brought home poor grades. Her father grounded her for a week.”
Ordered (Numbered) List
Use periods after the numbers in an ordered (numbered) list:
For example:
- Berlin
- Rome
- Istanbul
How to USe a Period Correctly When Linking Text
Use period at the end of linked text but do not link the period itself.
Example:
Avoid: See Chapter 3.
Correct Way: Chapter 3.
File Format
When punctuating file extensions, use a period BEFORE file formats:
“.pdf file” “.exe installer” “.jpg image”
More Info
| How to Punctuate Items Listed in a Table Cell or Unordered List |
| Ways to Punctuate a List |
| Writing and Punctuating Measurements Correctly |
