A semicolon (;) creates a pause stronger than a comma but weaker than a period. Its main job is to connect closely related ideas or clarify a complicated list.
1. Between two related independent clauses
Use a semicolon to join two complete sentences when their meanings are closely connected.
The meeting ended at noon; everyone went to lunch afterward.
Both sides could stand alone:
- The meeting ended at noon.
- Everyone went to lunch afterward.
The semicolon emphasizes the relationship between them. A period would also be correct, but a comma alone would not:
Incorrect: The meeting ended at noon, everyone went to lunch afterward.
This error is called a comma splice.
Use semicolons selectively. If the connection between the sentences is weak, a period is usually clearer.
2. Before a transitional word between complete sentences
Use a semicolon before words such as however, therefore, nevertheless, moreover, consequently, otherwise, and instead when they connect two independent clauses. Put a comma after the transitional word.
The forecast predicted sunshine; however, it rained all afternoon.
The application was incomplete; therefore, it could not be processed.
This differs from coordinating conjunctions such as and, but, or, so, yet, for, and nor. Those usually take a comma rather than a semicolon:
The forecast predicted sunshine, but it rained all afternoon.
3. To separate complicated items in a list
Use semicolons when list items already contain commas. This makes the boundaries between items clear.
The conference has attendees from Austin, Texas; Portland, Oregon; and Albany, New York.
Without semicolons, the sentence could make it seem as though six separate places were listed.
Another example:
Please invite the department head, who will open the event; the project manager, who will present the results; and the designer, who will demonstrate the product.
When not to use one
Do not use a semicolon:
-
Between a dependent clause and an independent clause:
Incorrect: Although it was raining; we went outside.
Correct: Although it was raining, we went outside. -
Before a simple explanation or list:
Incorrect: Bring; a coat, gloves, and a hat.
Correct: Bring a coat, gloves, and a hat. -
Automatically before words like “however”: A semicolon is appropriate only if complete sentences appear on both sides.
The plan was, however, too expensive.
No semicolon is needed because “The plan was” is not complete in this construction.
A quick test
For the most common use, look at the words on each side of the semicolon and ask:
- Could each side be a complete sentence?
- Are the two ideas closely related?
- Would a period also be grammatically correct?
If all three answers are yes, a semicolon is probably appropriate:
I have an early appointment; I should leave now.
Semicolons are useful, but they are optional in many cases. When unsure, separating the thoughts with a period is usually the safest choice.