Editing Tip: Semicolon Usage

A lot of good writers use the semicolon well; a lot of bad writers abuse it. There's one very common semicolon error; this one. -- Ben Yagoda

The semicolon (;) is one of my all-time favorite punctuation marks. It is most often used to draw attention to the connection between two related ideas. Another way to think about the semicolon is as a stand-in for the comma and conjunction combination (replacing “, and” or “, but”). The phrases on each side of the semicolon must be independent clauses (i.e., complete thoughts), and no conjunction is required.

Examples of semicolon usage

• The trial results were entered into the database; all records were coded to preserve anonymity.
• Ten patients were admitted with disease symptoms; two died within 48 hours.
• Pro-tip -- If all else fails, using a semicolon is a great way to get around starting a sentence with a number: The cohort consisted of 82 patients with Alzheimer's disease; 15 patients were under 55 years of age.

Semicolons are likewise used when joining two independent clauses with a conjunctive adverb, such as however, indeed, or therefore (i.e., any word/phrase that would be considered an introductory clause in a standalone sentence):

• The two species are closely related; however, Ursus maritimus is better adapted to cold weather.
• Contrary to our expectations, sales did not fall in the second quarter; indeed, we sold more widgets in April than in any other month.

Semicolons in a list

The semicolon can also be used instead of commas to separate items in a list when one or all of the items already contain commas. This usage is especially common in academic writing and can even be used in the Methods or Results sections. Note that when semicolons are used to separate items in a list, the final semicolon before and is required.

• The countries were divided into three groups based on their geography: China, South Korea, and Japan; the UK, the US, and Canada; and Germany, France, and Italy.
• Patients were excluded if they had a family history of drug or alcohol abuse; had kidney, heart, or liver disease; were pregnant or nursing; or were undergoing treatment for another psychiatric disorder.
• The participants averaged 36 hours of training (range, 22-57; median 32).
• The B-actin antibody (1:1000 dilution; Abcam, Cambridge, MA) was used as a control.

Using semicolons is an excellent way to introduce variety into the sentence structure in your writing. For a paragraph with many short, choppy sentences, linking two of those sentences with a semicolon can improve the overall flow of the text. Similarly, a long sentence with many clauses can often be divided with a semicolon to make it easier to read while still emphasizing the connection between ideas.

However, as with other less-straightforward sentence structures, these constructions should be used sparingly; readers will notice if every other sentence contains a semicolon. We hope that today's tips and examples help encourage you to use the semicolon in your own writing! If you have questions about using semicolons, send us an email. AJE wishes you the best!