The colon can be a pesky piece of punctuation – it’s definitely caused me a few head-scratching moments over the years. If, like me, you went to school in the days when teaching grammar was seriously out of fashion, you might find yourself unwittingly misusing the colon. It wasn’t until I trained as an English teacher - many moons ago – that I gained a handle on it. As an editor and proofreader, the colon is now part of my everyday bread and butter. I’ve become fond of it - when it behaves itself and doesn’t rear its head too often.
It turns out that the colon is really rather simple to use. In the Penguin Guide to Punctuation, Larry Trask sums this up nicely: ‘The colon (:) seems to bewilder many people, though it’s really rather easy to use correctly, since it has only one major use.’ That use is, as described in New Hart’s Rules, to point forward. It creates a pause or separation between two related ideas.
‘The colon points forward: from a premise to a conclusion, from a cause to an effect, from an introduction to a main point, from a general statement to an example.’
—New Hart’s Rules (4.5)
The colon points forward from a premise to a conclusion:
She had always been an optimist: she believed that everything would eventually work out for the best.
In this sentence, the premise (She had always been an optimist) is introduced before the colon, and the conclusion (she believed that everything would eventually work out for the best) follows, explaining the result of her optimism.
The colon points forward from a cause to an effect:
He forgot to set his alarm: as a result, he was late for work.
In this case, the cause (He forgot to set his alarm) is presented before the colon, and the effect (he was late for work) follows, explaining the result of the cause.
The colon points forward from an introduction to a main point:
There’s only one thing to remember about writing: clarity is key.
Here, the introduction (There’s one thing you need to remember about writing) sets up the statement, and the main point (clarity is key) follows, providing the essential idea being introduced.
The colon points forward from the general to the particular.
There are many ways to stay healthy: regular exercise, a balanced diet, and enough sleep are essential.
In this sentence, the general statement (There are many ways to stay healthy) is introduced before the colon, and the specific examples (regular exercise, a balanced diet, and enough sleep) follow, providing particular details that support the general claim. This is also an example of a colon being used to introduce a list.
Occasionally, this structure can be reversed:
Regular exercise, a balanced diet, and enough sleep: these are the keys to staying healthy.
In this case, the specific examples (regular exercise, a balanced diet, and enough sleep) come first, followed by the general conclusion or summary (these are the keys to staying healthy) after the colon. This reversal can be used for emphasis, drawing attention to the particular elements before concluding with the broader statement.
Minor Uses
- The colon can be used to separate a scripture reference from the specific verse when referencing the Bible (Psalm 23:1).
- The colon can be used to express ratio (4:1). However, ratios should be spelled out in formal writing.
- The colon can be used to separate hours from minutes when expressing time (7:30, 2:10, 14:00). This is standard in US English, while British English favours the full stop.
- The colon can be used to separate the title and subtitle of a book (The Quiet Revolution: How Small Things Can Transform Your Life). Even if there is no colon on the cover title, you should use one when referencing the book.
'Rules' to Remember
- The colon performs a function similar to these linking words/phrases: namely, that is, as. For example, for instance, because, as follows, therefore.
- The colon is almost always preceded by a complete sentence. However, what follows a colon need not be a complete sentence or contain a verb.
- When introducing a list, never use a hyphen after the colon (:-).
- Avoid using a colon to precede a linking word/phrase when introducing a list.
- Do not use a colon to introduce a list that completes a sentence formed by the introduction.
WRONG: My favourite writers are: Agatha Christie, Stephen King, and William Boyd.
RIGHT: My favourite writers are Agatha Christie, Stephen King, and William Boyd.
- There is no need to capitalise the word that follows the colon, unless it’s a proper noun (although a capital is generally preferred in US English). However, if more than one sentence follows the colon then the first word after the colon should be capitalised. It is best to avoid using more than one sentence after the colon, though – readers my interpret the colon to apply only to the first sentence. You can address this by using parenthetical numbering and a semicolon, or rewording to eliminate the need for more than sentence.
- As mentioned earlier, a colon should only follow on from a complete sentence. The exception to this is a list that is set off from the text.
Did You Know?
The colon (:) was first used in English writing around the fourteenth century, but it became more common in the sixteenth century, primarily due to the influence of printing and the need for clearer punctuation.
The colon is sometimes used in time notation (e.g., 12:30) to separate hours from minutes. This usage can be traced back to the fourteenth century, when medieval manuscripts began adopting this system.
In literature, especially in the eighteenth and nineteenth centuries, writers like Samuel Johnson and Jane Austen used the colon to create a more structured rhythm in their sentences.