When to Use a Colon: Rules and Examples
The colon can be a tricky punctuation mark. You’ve probably grasped periods, question marks, exclamation points, and commas – but the rules surrounding colons may seem a bit trickier.
There are two main ways to use colons:
- To introduce an item or a series of items.
- To replace a semi-colon between two independent clauses: the second clause should explain or expand on the first in some way.
As you can see, I’ve used both types of colon above.
Colons can trip writers up, though. Perhaps you’re not sure whether to use a capital letter after a colon, or you’re unsure how to structure a list of items that follows a colon.
We’re going to go through some key rules that will hopefully clear things up.
Rule #1: Use a Colon to Introduce One or More Items, When Punctuation is Required
Here are some examples of colons being used correctly, preceding an item or multiple items when the sentence requires punctuation at that point.
I needed just one thing: courage.
(Not “I needed just one thing courage.”)
Bring the following equipment: a torch, warm clothing, and waterproof boots.
(Not “Bring the following equipment a torch, warm clothing, and waterproof boots.”)
However, you should not use a colon if the sentence does not require punctuation.
For instance, the following sentences are correct without a colon:
I needed courage.
(Not “I needed: courage.”)
You should bring a torch, warm clothing, and waterproof boots.
(Not “You should bring: a torch, warm clothing, and waterproof boots.”)
Rule #2: Use a Colon Before Listing Items with Bullet Points
It you’re listing items line by line, you should use a colon to introduce the list – even if that same colon wouldn’t be required for a list in sentence form. Here’s an example:
You should bring:
- A torch
- Warm clothing
- Waterproof boots
Rule #3: Be Consistent With Punctuation of Bullet Points
When using a colon to introduce a list in this way, capitalization and ending punctuation aren’t always necessary.
If each item on the list is a complete sentence, you should always capitalize the first letter and finish with a period (or question mark or exclamation point, if appropriate). In other cases, though, it’s up to you whether or not you want to capitalize and use periods – just be consistent.
You should bring:
- A torch.
- Warm clothing!
- Waterproof boots.
This example is consistent because each item ends with a punctuation mark: either a period or an exclamation point.
Rule #4: Carefully Consider Capitalizing a Complete Sentence After a Colon
Some editors believe that it’s always best to capitalize a complete sentence that comes after a colon, like this:
He asked for help: He got it.
Others believe that you should generally avoid capitalizing in this way, instead preferring:
He asked for help: he got it.
Some would say that you don’t need to capitalize if the clause after the colon bears a close relationship to the clause before the colon, but would capitalize a general or formal statement, such as:
Remember what your mother taught you: If you can’t say anything nice, don’t say anything at all.
In these cases, it’s best to either consult the style guide for the publication you’re writing for, or to create a consistent style guide for your own work.
There are a couple of cases in which you should always capitalize the sentence after a colon, though.
When it’s a Complete or Full Sentence Quotation
The chair made an announcement: “This meeting will have to be postponed.”
In that example, “This” has to be capitalized because it’s the start of a full sentence quotation.
When the Information After the Colon Requires Two (or More) Sentences
The rules were inflexible: No running in the corridors. No shouting. Always walk on the right.
In this case, it makes sense to capitalize the first “No” because it’s the first of three full sentences.
Rule #5: Use a Colon to Introduce an Extended Quotation
Whether you’re writing an essay, a non-fiction book, or a blog post, there’ll be times when you want to quote someone else at some length (more than a sentence or two). This means using a “block quotation” that goes in its own standalone paragraph. This should normally be preceded by a colon, and should be indented from the left margin – some style guides also indent from the right margin.
In 26 Feel-Good Words, Michael wrote:
Some writers neglect the power of emotion when communicating their ideas, valuing logic more than others do, and assuming that everyone thinks like they do – that careful reasoning is enough to convince readers and make points. But even the ancient Greek philosopher Aristotle, who was no enemy of reason, taught that stimulating emotion in your audience can be the key to persuading them.
Rule #6: Use a Colon After the Salutation in a Business Letter (Depending on Where You Live)
In American and Australian usage, the salutation (greeting) should be followed by a colon in formal correspondence – this applies whether you’re using someone’s surname or first name:
Dear Mr Richardson:
Informal or personal correspondence uses a comma in place of this colon.
In British English, though, you should use a comma after the salutation – never a colon – for formal business letters as well as for informal letters.
Colons can take a bit of practice, so try using one (or more!) in the next piece that you write. You’ve probably already used them to introduce lists, but how about structuring a sentence that has two independent clauses joined by a colon? Drop us a comment below to share your examples.
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