The Colon vs. The Semicolon

What is the difference between a colon and a semicolon? Good question! In fact, the misuse—and frequent substitution—of these two punctuation marks is one of the most common grammatical errors we see. In fact, the two are so widely misunderstood that we have even caught university professors mistaking them! It’s important to remember that the colon and the semicolon are not interchangeable. We’ll take each one separately and try to provide some examples highlighting the difference between the colon and the semicolon.

Let’s begin with dreaded semicolon!

Use number one

The semicolon is used to join two independent clauses in compound sentences. An independent clause is simply a clause that can stand by itself, as its own complete sentence. Here are some examples:  

• The parade was fantastic; all the kids had a great time. 

• We started our hike early in the morning; George led the way up the mountain.

These sentences could also be written as two entirely distinct sentences, separated by a period. However, since they are similar, a semicolon is often a helpful way of alerting the reader to their relationship. A word of advice: use the semicolon sparingly. Excessive use of the semicolon can be very irritating to readers (mainly because your audience might not know what it means!).

Frequently, a transition word (such as therefore, furthermore, moreover, or thus) is placed after a semicolon in order to more directly help the reader understand the relationship between two independent clauses. We highly recommend using transition words, because they significantly improve the flow of your writing.

• Michael drank a little too much last night; he did not feel well this morning.
• Michael drank a little too much last night; therefore, he did not feel well this morning.

• Jenny has studied in France for two years; she can speak French fluently.
• Jenny has studied in France for two years; thus, she can speak French fluently. 

Remember, when using a transition word in this case, it is always necessary to precede it with a semicolon and follow it with a comma.

Use Number Two

Semicolons are also a helpful way to distinguish among different items in a list, especially when a comma in already present. For example:

• The esteemed panel consisted of five professors from five different academic backgrounds, including Rob Tichman, Theatre; Bob Osborne, Economics; Suzy Winthrope, Linguistics; Carl Leven, Political Science; and Pearl Shalfont, Biological Science.

• I can’t say enough about Tony! He is an excellent friend, mentor and father; an accomplished pianist; a great writer; and a world class intellectual. 

Frequent Misuse of Semicolons

Semicolons are very often used in place of a comma or an em-dash. This is incorrect. These punctuation marks are not interchangeable. This is an embarrassing mistake, so avoid it!

• Incorrect: The wind blew viciously as the storm clouds floated overhead; signaling the coming storm.

• Correct: The wind blew viciously as storm clouds floated overhead, signaling the coming storm.

• Incorrect: The sea was calm, the sand was soft and the waves crashed softly along the coastline; a beautiful day indeed.

• Correct: The sea was calm, the sand was soft and the waves crashed softly along the coastline; it was a beautiful day indeed.

• Correct: The sea was calm, the sand was soft and the waves crashed softly along the coastline—a beautiful day indeed. 

Never use a semicolon to begin a list. This is the most common error we see and it is often used on professional documents. The professional service firm Ernst & Young repeatedly makes this mistake on its homepage!

• Incorrect: There are four prerequisites for the econometrics course; statistics 101, calculus 240, political science 120 and economics 201.

• Correct: There are four perquisites for the econometrics course: statistics 101, calculus 240, political science 120 and economics 201.

Now let’s move on to the colon!

The main uses of a colon are: to precede a list (wink, wink), to distinguish certain elements of a sentence, to separate minutes and hours when writing the time, and to end a salutation. Let’s take each one separately.

Use Number One

Use a colon (not a semicolon!) to introduce a list.

• Doctors need an understanding of many different subjects: Biology, Chemistry, Anatomy and Virology.

• Some of Walter Isaacson’s excellent books are: Ben Franklin, Steven Jobs, Einstein and American Sketches

Use Number Two

Use a colon to distinguish an example, or to highlight a particular point after an independent clause.

• Bankers in the late 2000s did not understand one very important lesson: Derivative investments are very unpredictable!

• To open or close a soda bottle you need to remember one simple saying: Righty tighty, lefty loosey!

Use Number Three

Use a colon to separate minutes from hours when writing the time.

• 3:45

• 8:00

Use Number Four

You can use a colon after the salutation of a formal letter.

• Dear Mr. Robinson:

• Dear Sir or Madam:

Interesting fact: Instead of using a colon after formal salutations, Russians use an exclamation point! This would be pretty strange—and maybe even off-putting—to see in English!

• Dear Mr. President!

• Dear University Proofreading!

We hope you have a firm grasp on the difference between the colon and the semicolon! If you have any questions, or just want to try some practice sentences to test your understanding, get it touch with us! We're always happy to hear from our friends on the web! 

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