Colons and semicolons are two kinds of punctuation marks. The colon (:) consists of two periods, one above the other, and is preceded by an independent clause (a clause that can work as a standalone sentence) though not followed by one.
For example:
- She kept saying: “I’m really hungry.”
- They wanted to visit three European cities: Paris, Athens, and Rome.
The semicolon (;) consists of a comma with a period above it and is used to join two independent clauses without using a conjunction. Like the comma, the semicolon indicates an audible pause – slightly longer than the comma’s but shorter than the full stop of a period.
For example:
- We made too many mistakes; we lost the game.
- Call me tomorrow; we can go over the contract in detail then.
The Appropriate Use of Colons
Colons are generally used:
1. To introduce, announce, or draw attention to a quotation, a list, an example, or a noun or noun phrase
Look at the following examples:
i. Colon in quotations
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- As Dr. Johnson so aptly said: “Patriotism is the last refuge of a scoundrel.”
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- The leader of the aliens said: “We come in peace. Put away your weapons.”
ii. Colon in lists
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- We revisited many of the fundamentals in our calculus class: limits and continuity, derivatives, integrals, and differential equations.
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- You need the following ingredients to bake a cake: sugar, butter, flour, eggs, milk, and baking powder.
iii. Colon in examples
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- The grocery store stocks many different types of apples: Granny Smith, Fuji, Pink Lady, Honeycrisp, Envy, and Gala, to name a few.
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- We love playing a variety of board games on Friday game nights: Monopoly, Scrabble, Battleship, Clue, and Risk.
iv. Colon in noun or noun phrase
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- Little Jane treasured two things above everything else: her toys and her books.
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- My partner gives me the things I need most: companionship and space.
2. To join two different sentences with closely related content
For example:
- Love is like war: easy to begin, hard to stop.
- Mason got what he worked so hard for: he really earned his promotion.
3. As part of common writing conventions
i. With numbers
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- Units of time – 5:45 a.m.
- Ratios – 2:1
- Bible chapters – Psalm 12:6
ii. In bibliography entries
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- Jaynes ET. Probability theory: the logic of science. Cambridge (UK): Cambridge University Press; 2003.
iii. Separating titles from subtitles
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- Conquering the Himalayas: A Mountain Climber’s Memoir
The Erroneous Use of Colons
1. Between a preposition and its object
For example:
- My favorite subjects in school are: physics, chemistry, algebra, and calculus.
2. Between a verb and its object or complement
For example:
- Some of the best tomatoes in the world are: those that are grown in Southern Germany.
3. After words and phrases like “including,” “such as,” “especially,” etc.
For example:
- There are many different types of dog breeds, such as: beagle, dalmatian, foxhound, dachshund, and pitbull.
Excessive use of colons can disrupt readability, so it’s best to use them sparingly.
The Appropriate Use of Semicolons
Semicolons are generally used:
1. To separate items in a list, when the list already contains commas
For example:
- I bought juicy, ripe apples; firm, luscious pears; and ripe, yellow bananas at the store.
If commas are used instead of semicolons to separate these items, the sentence will look like this:
- I bought juicy, ripe apples, firm, luscious pears, and ripe, yellow bananas at the store.
Semicolons help readers identify how many items are in the list and which words go together.
2. To join two independent clauses
Using a semicolon between two independent clauses unites them while keeping them somewhat separate. Thus, readers can easily determine which idea belongs to which clause while noting the close relationship between the two.
For example:
- I went to the bookstore today. I bought several things; books, magazines, and journals were on sale.
Semicolons, however, shouldn’t be used to connect more than two clauses. Also, the first word of the second independent clause needn’t be capitalized.
Another important thing to note is that semicolons link two closely related independent clauses. If one or both clauses cannot stand on their own, using a colon would be more appropriate.
A good rule of thumb is to use a semicolon if the two clauses are loosely connected but do not offer a sequence of ideas. However, if they are sequential in thought, a colon would be a better fit.
