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Understanding Colons, Semicolons & Periods

Writing requires a variety of tools for communicating ideas, with a sentence serving as the most basic unit for communicating a complete thought. At its most rudimentary, a writer always signals the end of a completed statement sentence with a period. Multiple sentences can be strung together to communicate a more complex vision of an idea. However, at times it may be more effective, clear, efficient, or stylistically pleasing to join multiple parallel ideas with either of the following punctuation marks:

  • Colons – Typically, these are used to expand an idea with a list of items or when joining two or more independent clauses.
  • Semicolons – Typically, a semicolon is used to join two independent clauses that are tightly connected in concept.

When used correctly, a diversity of connecting and concluding punctuation marks can add depth, efficiency, and clarity to a writer’s argument.

Colon or Semicolon?

Colon Punctuation

There are many different uses for a colon in this case: initiating a series, initiating a quote, commenting on a clause, or in a business address.

A colon

A colon

Initiating a Series

Colons are most commonly used to begin a series. A series is a list of things, separated by commas, in a way that the colon seems to stand for the idea “which are” or “and they are.”

Example: There are four main islands that comprise the country of Japan: Hokkaido, Honshu, Shikoku, and Kyushu.

Notice that in this case, the colon could be replaced with “which are”. This is the most common of uses for the colon. One very common mistake is to include “are” in the sentence. The following sentence is incorrect:

Example: The four main islands that comprise the country of Japan are: Hokkaido, Honshu, Shikoku, and Kyushu.

In this case, there would be no colon.

Example: The four main islands that comprise the country of Japan are Hokkaido, Honshu, Shikoku, and Kyushu.

The sentence above is correct.

Initiating a Quote

Colons are also commonly used to initiate a quote when the first clause is an independent clause (or a complete sentence) or when the quote itself is an independent clause.

Example: He lived by Ernest Hemingway’s motto: “The way to make people trustworthy is to trust them.”

Commenting on a Clause

More advanced usage of the colon is somewhat similar to the semicolon (splitting two independent clauses). In this case, however, the clause after the colon should comment on or relate strongly to the first clause.

Example: Edgar Allen Poe’s cause of death was never determined: alcohol is, however, thought to be a contributing factor.

In a Business Address

While many cordial letters begin with “Dear Ms. —–,” using a comma, in business letters it is more common to use a colon, as in “Mr. —-:”

Semicolon Punctuation

Semicolons, on the other hand, have two main uses: to link two closely-related independent clauses and to create a multi-leveled series.

A semicolon

A semicolon

Linking Independent Clauses

Two independent clauses or sentences can be linked due to the closeness of their content. A period can be exchanged for a semicolon in most cases.

Example: I love to spend time at the high school on Saturdays; it’s so quiet without all the students and teachers there.

Creating a Multi-leveled Series

When there are commas within commas in a series, the semicolons replace the commas that separate phrases. The outside commas become semicolons so that the readers understand the difference between separating the different series members and the comma separations inside of the clauses.

Example: My three favorite astronauts are already famous: Buzz Aldrin, who walked on the moon; Sally Ride, who was bound to become the first teacher in space; and Yuri Gagarin, the first man in space.

This usage of the semicolon is the least known and the most technical. Many writers don’t know how to express a comma within a comma.

Example: There are three ways to separate independent clauses without subordinating words and commas: the period, which is used in nearly all cases; the semicolon, which is used when the two clauses are close in meaning; and the colon, which shows that the second clause is commenting or expanding on the first.

How to Use the Colon and Semicolon

The colon and semicolon are both strongly related to the comma and period. The colon operates as a comma in the introduction of a series and in a business address, but also can separate two independent clauses when one comments on the other. The semicolon is also like something between a comma and a period: it can separate two closely linked independent clauses like a period, but doing the same thing with a comma would create a grammatically incorrect comma splice.

Connecting Two Independent Clauses

Here are further examples of ways to link independent clauses with colons or semicolons.

  • Colon – Linking a quote introduction with an independent clause that is a quote – The umpire said to the player: “You’re out!”
  • Colon – Linking two independent clauses where the second one comments on or emphasizes the first – The Scarlet Letter is one of the first blockbuster American novels: the novel’s first printing of 2,500 books sold out in 10 days.
  • Semicolon – Linking two independent clauses that are closely linked in meaning or content – I fell in the bath yesterday; I feared that I broke my shoulder, but it was just a bruise.

Connecting Transitional Words and Phrases

Transitional words (such as moreover, therefore, however, alternatively, etc.) refer to words that emphasize, contrast, order, or compound meaning between two independent phrases. This is done with a semicolon splitting the independent clauses, the transitional word, and a comma.

Example: The army believed that the battle would be bloody; however, when they arrived, they found the enemy had fled.

Example: You can use the voucher to select the outfit that fits you; alternatively, you can go to the cashier and receive the voucher’s value in cash.

Example: Living in the South means hot summers and cool winters; moreover, it only snows an average of once a year.

Period Punctuation

It is grammatically correct to use periods to separate practically all independent clauses. However, using a semicolon or a colon with independent clauses shows a more nuanced relationship between two independent clauses. Semicolons are used between these clauses in place of a period when their content is similar; a semicolon emphasizes that the two sentences are close in meaning. Colons, on the other hand, are used when the second clause is commenting on the first: this type of linking of clauses with a colon is common in academic and researched writing. Finally, colons are also frequently used when there are two independent clauses where the second is a quote. So, use colons correctly in your writing. Your teacher will notice it and compliment you: “You’ve done an excellent job!”

Lesson Summary

Many students refrain from using semicolons and colons because they don’t know how the two work, so many writers stick heavily to the period as a separator between two independent clauses. However, the use of colon and semicolons are very important in composition. That being said, the colon has a variety of uses: it can separate two independent clauses where one comments on the other, it can be used in a business address, it can be used to split an introduction to a quote and a quote that is an independent clause, and it can introduce a series. A semicolon, on the other hand, can be used to separate two independent clauses that are linked in meaning or it can function as a comma in a multi-layered series. Experimenting and becoming comfortable with the use of colon and semicolon punctuation marks shows maturity in writing and should be practiced and used by writers.

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