The colon (:) seems to bewilder many people, though it's really rather easy to use correctly, since it has only one major use. But first please note the following: the colon is never preceded by a white space; it is always followed by a single white space in normal use, and it is never, never, never followed by a hyphen or a dash — in spite of what you might have been taught in school. One of the commonest of all punctuation mistakes is following a colon with a completely pointless hyphen.
The colon is used to indicate that what follows it is an explanation or elaboration of what precedes it. That is, having introduced some topic in more general terms, you can use a colon and go on to explain that same topic in more specific terms. Schematically:
More general: more specific
A colon is nearly always preceded by a complete sentence; what follows the colon may or may not be a complete sentence, and it may be a mere list or even a single word. A colon is not normally followed by a capital letter in British usage, though American usage often prefers to use a capital. Here are some examples:
- Africa is facing a terrifying problem: perpetual drought.
[Explains what the problem is.]
- The situation is clear: if you have unprotected sex with a stranger, you risk AIDS.
[Explains what the clear situation is.]
- She was sure of one thing: she was not going to be a housewife.
[Identifies the one thing she was sure of.]
- Mae West had one golden rule for handling men: "Tell the pretty ones they're smart and tell the smart ones they're pretty."
[Explicates the golden rule.]
- Several friends have provided me with inspiration: Tim, Ian and, above all, Larry.
[Identifies the friends in question.]
- We found the place easily: your directions were perfect.
[Explains why we found it easily.]
- I propose the creation of a new post: School Executive Officer.
[Identifies the post in question.]
Very occasionally, the colon construction is turned round, with the specifics coming first and the general summary afterward:
- Saussure, Sapir, Bloomfield, Chomsky: all these have revolutionized linguistics in one way or another.
Like all inverted constructions, this one should be used sparingly.
While you're studying these examples, notice again that the colon is never preceded by a white space and never followed by anything except a single white space.
You should not use a colon, or any other mark, at the end of a heading which introduces a new section of a document: look at the chapter headings and section headings in the present document. It is, however, usual to use a colon after a word, phrase or sentence in the middle of a text which introduces some following material which is set off in the middle of the page. There are three consecutive examples of this just above, in the second, third and fourth paragraphs of this section.
The colon has a few minor uses. First, when you cite the name of a book which has both a title and a subtitle, you should separate the two with a colon:
- I recommend Chinnery's book Oak Furniture: the British Tradition.
You should do this even though no colon may appear on the cover or the title page of the book itself.
Second, the colon is used in citing passages from the Bible:
- The story of Menahem is found in II Kings 15:14–22.
Observe that, exceptionally, the colon is not followed by a white space in Biblical references.
Third, the colon may be used in writing ratios:
- Among students of French, women outnumber men by more than 4:1.
In formal writing, however, it is usually preferable to write out ratios in words:
- Among students of French, women outnumber men by more than four to one.
Fourth, in American usage, a colon is used to separate the hours from the minutes in giving a time of day: 2:10, 11:30 (A). British Eng lish uses a full stop for this purpose: 2.10, 11.30.
Copyright © Larry Trask, 1997
Maintained by the Department of Informatics, University of Sussex