Unpacking CMOS: Semicolons vs. Colons

Emily Fahey Editing Tips, Grammar, Writing Tips

The difference between semicolons and colons can be challenging, and it is not uncommon to see them used interchangeably; hence, they are often used incorrectly. Let’s dive into the unique uses for each punctuation mark.

Use of the Semicolon

Common Use

Semicolons are commonly used between two independent clauses. The semicolon signals a closer connection between these clauses than the use of a period would.

  • My child refuses vegetables; I’ve taken to blending them into a soup to get her to eat them.
  • The gray clouds loomed ominously; it was far too dangerous to take the boat out.

In the examples above, the phrases preceding and following the semicolon could stand on their own, as they each have a subject and a verb. However, using a semicolon provides a clean flow to sentences that would otherwise feel wordy. The use of the semicolon can sometimes be subjective, but it is a great tool for efficient writing.

Following an Adverb

When certain adverbs are used to join two independent clauses, the adverb should be preceded by a semicolon rather than a comma. These adverbs include: however, thus, hence, indeed, accordingly, besides, and therefore. A comma is often used after the adverb but is unnecessary if the sentence seems effective without it, as seen in the second example here.

  • The artist ran out of cerulean blue before her abstract art was complete; however, adding a new shade of blue increased the vibrancy of the finished piece.
  • Marian started the chocolate muffin recipe before checking the ingredient list; thus, she had to substitute bananas because she was out of eggs.

Similarly, semicolons may be used before expressions such as that is, for example, and namely when they introduce an independent clause.

Using a semicolon provides a clean flow to sentences that would otherwise feel wordy. #cmos #unpackingcmos #writingtips Click To Tweet

Indexes, Citations, and Titles

Proper use of the semicolon is more complex in relation to indexes, citations, and titles. The Chicago Manual of Style expands on these finer points of usage, but here is a quick primer to start with.

  • Within indexes, semicolons are used to separate subentries and sub-subentries. If there is more than one cross-reference, these are also separated by semicolons.
  • Within text citations, if there are two or more references within a single parenthetical, the references are separated by semicolons. (An important exception to note is that when referencing two or more works by the same author, a comma is used rather than a semicolon.)
  • When there are two subtitles within a cited work, a colon precedes the first subtitle and a semicolon precedes the second.

Use of the Colon

To Amplify or Illustrate

A colon is used when the sentence introduces an element or a series of elements. CMOS recommends that colons be used sparingly and only to emphasize that the phrase after the colon illustrates or amplifies the first part of the sentence.

  • The toddler’s tiny purse held just three items: a pink crayon, a sparkly green hair clip, and a tiny toy dinosaur.
  • His pizza order included the most pungent toppings on the menu: onions, anchovies, and extra garlic.

To Reinforce the Phrase As Follows

Colons can also serve to reinforce the phrases as follows or the following within a sentence.

  • When you go to the store, please pick up the following: fresh strawberries, heavy cream, and angel food cake.
  • We need to complete tomorrow’s errands as follows: pick up the dry cleaning, drop off the library books, and go grocery shopping.

In Formal Writing

At the beginning of a professional document or written speech, the colon may be used after identifying the addressees.

  • To Whom It May Concern:
  • Distinguished Faculty, Alumni, Students, and Parents:

Speech and Quotations

Remember that when colons are used to introduce speech in dialogue or to introduce a quotation, the sentence following the colon should start with a capital letter.

  • Hamlet: To be or not to be, that is the question.
  • John Knowles’ classic novel, A Separate Peace, begins with a sense of disorienting nostalgia: “I went back to Devon School not long ago and found it looking oddly newer than when I was a student there fifteen years before.”

Notes and Bibliography

Colons are used to separate main titles from subtitles. The subtitle always begins with a capital letter.

  • Van der Kolk, Vessel. The Body Keeps the Score: Brain, Mind, and Body in the Healing of Trauma. New York: Viking Penguin, 2014.
  • Bonney, Grace. In the Company of Women: Inspiration and Advice from over 100 Makers, Artists, and Entrepreneurs. New York: Artisan, 2016.
Use colons sparingly to amplify or illustrate elements of your sentence. #cmos #unpackingcmos #writingtips Click To Tweet


When a main heading is followed by subentries, a colon is used before the first subheading, as well as being used in cross-reference to a subentry.

Uncommon Use

A correct, though rare, use of the colon is to use it in place of a period to introduce a series of related sentences.

  • The birthday party was a success until someone upset the chocolate fountain: The chocolate flooded the dessert table and ruined the white tablecloth. The children ran gleefully toward the spill and had to be carried away, wailing at the indignity. And, after the party, the host found tiny chocolate paw prints that led to the offended cat who was unlucky enough to be beneath the table when the spill occurred.

When Not to Use a Colon

CMOS cautions that colons are never to be used after words and phrases such as that is, namely, or for example, where a comma is the appropriate choice.

  • INCORRECT: Many plants can thrive with little water, for example: succulents and cacti.
  • CORRECT: Many plants can thrive with little water; for example, succulents and cacti.

Semicolons and colons can be tricky pieces of punctuation to navigate, but The Chicago Manual of Style is truly a comprehensive resource and beneficial tool for any writer.


Need a little more help with the complexities of punctuation? Our CMOS-loving team is here to help


About the Author

Emily spent ten years as a fundraising professional in higher education and public media and began moonlighting as a copywriter for the Scribe Source in 2014. She left the nonprofit world in 2019 to focus on copywriting, editing, and blog management for the Scribe Source.