The Colon and the Semicolon
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 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.
Finally, the colon is used in formal letters and in citing references to published work.
The semicolon (;) has only one major use. It is used to join two complete sentences into a single written sentence when all of the following conditions are met:
(1) The two sentences are felt to be too closely related to be separated by a full stop;
(2) There is no connecting word which would require a comma, such as and or but;
(3) The special conditions requiring a colon are absent.
Here is a famous example:
It was the best of times; it was the worst of times.
A semicolon can always, in principle, be replaced either by a full stop (yielding two separate sentences) or by the word and (possibly preceded by a joining comma). Thus Dickens might have written:
It was the best of times. It was the worst of times. or
It was the best of times, and it was the worst of times.
The use of the semicolon suggests that the writer sees the two smaller sentences as being more closely related than the average two consecutive sentences; preferring the semicolon to and often gives a more vivid sense of the relation between the two. But observe carefully: the semicolon must be both preceded by a complete sentence and followed by a complete sentence. Do not use the semicolon otherwise:
*I don't like him; not at all.
*In 1991 the music world was shaken by a tragic event; the death of Freddy Mercury.
*We've had streams of books on chaos theory; no fewer than twelve since 1988.
*After a long and bitter struggle; Derrida was awarded an honorary degree by Cambridge University.
These are all wrong, since the semicolon does not separate complete sentences. (The first and last of these should have only a bracketing comma, while the second and third meet the requirements for a colon and should have one.) Here are some further examples of correct use:
Tolkien published The Hobbit in 1937; the first volume of The Lord of the Rings followed in 1954.
The Cabernet Sauvignon grape predominates in the Bordeaux region; Pinot Noir holds sway in Burgundy; Syrah is largely confined to the Rhone valley.
Women's conversation is cooperative; men's is competitive.
If a suitable connecting word is used, then a joining comma is required, rather than a semicolon:
Women's conversation is cooperative, while men's is competitive.
A semicolon would be impossible in the last example, since the sequence after the comma is not a complete sentence.
Note, however, that certain connecting words do require a preceding semicolon. Chief among these are however, therefore, hence , thus, consequently, nevertheless and meanwhile:
Saturn was long thought to be the only ringed planet; however, this is now known not to be the case.
The two warring sides have refused to withdraw from the airport; consequently aid flights have had to be suspended.
Observe that in these examples the sequence after the semicolon does constitute a complete sentence. And note particularly that the word however must be separated by a semicolon (or a full stop) from a preceding complete sentence; this is a very common mistake.
There is one special circumstance in which a semicolon may be used to separate sequences which are not complete sentences. This occurs when a sentence has become so long and so full of commas that the reader can hardly be expected to follow it without some special marking. In this case, we sometimes find semicolons used instead of commas to mark the most important breaks in the sentence: such semicolons are effectively being used to mark places where the reader can pause to catch his breath. Consider the following example:
In Somalia, where the civil war still rages, western aid workers, in spite of frantic efforts, are unable to operate, and the people, starving, terrified and desperate, are flooding into neighbouring Ethiopia.
This sentence is perfectly punctuated, but the number of commas is somewhat alarming. In such a case, the comma marking the major break in the sentence may be replaced by a semicolon:
In Somalia, where the civil war still rages, western aid workers, in spite of frantic efforts, are unable to operate; and the people, starving, terrified and desperate, are flooding into neighbouring Ethiopia.
Such use of the semicolon as a kind of "super-comma" is not very appealing, and you should do your best to avoid it. If you find one of your sentences becoming dangerously long and full of commas, it is usually better to start over and rewrite it, perhaps as two separate sentences:
In Somalia, where the civil war still rages, western aid workers, in spite of frantic efforts, are unable to operate. Meanwhile the people, starving, terrified and desperate, are flooding into neighbouring Ethiopia.
In any case, don't get into the habit of using a semicolon (or anything else) merely to mark a breathing space. Your reader will be perfectly capable of doing his own breathing, providing your sentence is well punctuated; punctuation is an aid to understanding, not to respiration.
The Colon and the Semicolon Compared
Since the use of the colon and the semicolon, although simple in principle, presents so many difficulties to uncertain punctuators, it will be helpful to contrast them here. Consider first the following two sentences:
Lisa is upset. Gus is having a nervous breakdown.
The use of two separate sentences suggests that there is no particular connection between these two facts: they just happen to be true at the same time. No particular inference can be drawn, except perhaps that things are generally bad. Now see what happens when a semicolon is used:
Lisa is upset; Gus is having a nervous breakdown.
The semicolon now suggests that the two statements are related in some way. The likeliest inference is that the cause of Lisa's annoyance and the cause of Gus's nervous breakdown are the same. Perhaps, for example, both are being disturbed by building noise next door. (Remember, a semicolon connects two sentences which are related.) Now try it with a colon:
Lisa is upset: Gus is having a nervous breakdown.
This time the colon shows explicitly that Gus's nervous breakdown is the reason for Lisa's distress: Lisa is upset because Gus is having a nervous breakdown. (Remember, a colon introduces an explanation or elaboration of what has come before.)
Consider another example:
I have the answer. Mike's solution doesn't work.
Here we have two independent statements: my answer and Mike's solution may possibly have been directed at the same problem, but nothing implies this, and equally they may have been directed at two entirely distinct problems. Now, with a semicolon:
I have the answer; Mike's solution doesn't work.
The semicolon shows that the two statements are related, and strongly implies that Mike and I were working on the same problem. Finally, with a colon:
I have the answer: Mike's solution doesn't work.
This time the use of the colon indicates that the failure of Mike's solution is exactly the answer which I have obtained: that is, what I have discovered is that Mike's solution doesn't work.
If you understand these examples, you should be well on your way to using colons and semicolons correctly.
Summary of colons and semicolons:
• Use a colon to separate a general statement from following specifics. • Use a semicolon to connect two complete sentences not joined by and, or, but, yet or while