Definition: The semicolon is a mark that looks like a period above a comma (;). It signals a more complete break than a comma, but not as complete as a period break. It's a "halfway-in-between" mark. It's used to show that two sentences are related in some way.
Joining Independent Clauses Without a Conjunction
When joining two independent clauses to make a compound sentence, a semicolon can be used instead of the comma and conjunction. This only works if the relationship between the sentences is close and clear.
I brought my umbrella, but I left it in the car.
I brought my umbrella; I left it in the car.
Remember: Connecting two independent clauses with a comma is always incorrect and creates what's called a comma splice. One way to fix a comma splice is to replace the comma with a semicolon. However, it's best to use semicolons sparingly. Often it's better to use either a comma plus a conjunction or just a period.
Joining Independent Clauses that Contain Commas
If at least one of the independent clauses in a compound sentence contains commas of its own, it's usually better to use a semicolon instead of a comma between clauses. Doing so helps avoid confusion. Just remember to remove the conjunction, unless it's a transitional conjunction (you'll learn about how to use those in the next section).
Comma + conjunction
My cousin just had a baby, and I hope to go visit her sometime this summer.
Semicolon with no conjunction
My cousin, who recently moved to London, England, just had a baby; I hope to go visit her sometime this summer.
You've probably already learned how to use transitional expressions to connect two independent clauses. Usually the first independent clause ends with a period, and the next clause starts with a transition plus a comma. Sometimes you can use a semicolon instead of a period if you want to show a closer link between the two clauses. If you choose to use a semicolon, the first letter of the transitional expression will be lowercase.
I have always liked bats. In fact, they are my favorite animals.
I have always liked bats; in fact, they are my favorite animals.
- There are other transitional expressions that can be used after a semicolon, such as however, moreover, and therefore, among others.
Series with Commas vs. Series with Semicolons
If the items in a series have their own commas, the series commas become semicolons to make the sentence easier to read.
Series with commas
I bought a scarf in Paris, cheese in Cheddar, a painting in Toledo, and a pair of earrings in Munich.
Series with semicolons
I bought a scarf in Paris, France; cheese in Cheddar, England; a painting in Toledo, Spain; and a pair of earrings in Munich, Germany.