When to use the colon and semicolon. The colon is a punctuation mark that is used to precede a list of items, a quotation, expansion or explanation. It marks the flow of an idea from the first statement to the second. Usually, it links a general or introductory statement to an example, or a cause to an effect or a premise with a conclusion.
Use a colon:
- To precede a list.
- To introduce a long quotation (say, of more than three lines in length).
- Between two sentences when the second sentence explains, amplifies or illustrates the first sentence.
Do not capitalise the first word of the second sentence. However, if two or more sentences follow the colon, capitalise the first word of each sentence following the first.
Use the colon where the second sentence amplifies on the first:
- She wondered if he could possibly be the man in the Mitsubishi but then dismissed it: he was obviously in the peak of health, with no outward show of injury.
To express a strong contrast:
- God creates: man destroys.
To introduce a climax or concluding clause:
- After thinking over his options, he finally came to a decision: he signed up for college.
The colon is also sometimes used to indicate more emphasis in indirect speech. Thus:
- The madman screamed: “I am not mad! The voice of God commanded me to slay.”
- The principle parts of English are: present tense, past tense and past participle.
- The three students who came to the seminar are: Clinton, Bush and Maud.
Between sentences grammatically independent but closely connected in sense:
- Study to acquire the habit of thinking: no study is more important.
As we mention in the section on quoting speech, a colon should be used when the person’s dialogue amounts to: a list; a statement; a quote from some source; to conform to the colon rule; or to relate the unspoken part at the end. Here are some examples (all from the novel Red Moon, by Nigel Benetton):
1] A list:
- ‘There are three differences in anatomy, as a matter of fact,’ Pledger added, by way of stopping her talking: ‘the blood; the method of breathing; and, some of the bone structures. They don’t have a patella.’
- He had the usual items: ‘One science time-piece,’ Harcourt said into the recorder.
- ‘They said the air was full of white powder. One of them said it was like…’ she paused to leaf through some papers, pulled out a page, and read from a highlighted paragraph: ‘talcum powder, that it was light and took a long time to settle. Another witness said people looked as though they were covered in flour.’
2] A statement:
‘Listen to this,’ he went on, reading from the back of the report: ‘subjects, mostly male from around the age of 25, are selected for conditioning, then targeted by special agents and—get this—“seeded” into the programme.’
3] A quote:
It made Ellerton angry at remembering the careless remark made by some low-level administrator the other day: ‘Well, Dr Ellerton, since you have so many stations closing, surely you now have enough money for that lab work you do down in those dungeons of yours.’
4] The colon rule:
A subtle use of the colon is when the following dialogue amplifies on the first (an important use of the colon as we discussed elsewhere). For example:
- ‘Well, it’s enough to cloud his judgment.’ Alpern paused: ‘having an affair that is.’
5] Unspoken part at the end:
- Ellerton took the device, looked at it for a moment, then looked at Pledger. In a sudden moment of decision, he passed it over to Pledger and mouthed the words: I’m not here.
The semicolon represents a pause greater than a comma, but less than a full stop. In other words, see it as the halfway point between a comma and a full stop. It is preferred where using a full stop seems too abrupt. It can be used instead of a comma in a sentence to indicate a stronger division. The words either side of the semicolon must be a full sentence in their own right. Further, the sentences must have connected thoughts.
- When I finish here, I will be glad to help you; and that is a promise I will keep.
- If she can, she will attempt that feat; and if her husband is able, he will be there to see her.
- He felt he did not like this promise of peril, this prospect of enormous responsibility; he had visualised nothing like this when he drove up at noon that day so gaily to receive his orders.
The semicolon is also used to separate the clauses of a compound sentence when they contain a comma. For example:
- He was a brave, large hearted man; we all respected him.
And the semicolon is used to separate a series of loosely related clauses. Thus:
- Her court was pure; her life serene.
- God gave her peace; her land reposed.
- Today we love what tomorrow we hate; today we seek what tomorrow we shun.
You can use a semicolon in place of a period to separate two sentences where the conjunction has been left out. In other words, if you have a long sentence combining two sentences with the conjunction “and”, you can delete the “and” and replace it with a semicolon (provided, of course, it makes sense!).
It is preferable to use a semicolon before sentences beginning with introductory words such as: “even so”, “for example”, “for instance”, “however”, “namely”, “nevertheless”, “that is”, “then”, “therefore”, “i.e.”, and, “e.g.”; but they must introduce a complete sentence. It is also preferable to use a comma after the introductory word. Thus:
- He took great care; even so, he made a few errors.
- You will want to bring many backpacking items; for example, sleeping bags, pans, and warm clothing will make the trip better.
- As we discussed, you will bring two items; i.e., a sleeping bag and a tent are not optional.
The semicolon is used to describe a sequence of actions or different aspects of the same topic:
- There was a sharp, bracing air; the ground was dry; the sea was crisp and clear.
Finally, use a semicolon to suggest a contrast:
- I like swimming; my sister hates it.
By Nigel Benetton, science fiction author of Red Moon Burning and The Wild Sands of Rotar
Last updated: Monday, 13th January 2020