Colons are used to introduce one sentence or sequence of sentences.
In essays, a colon will commonly be used to introduce quotations, lists or explanations. A colon can also be used for rhetorical effect to add emphasis to a point being made.
Colons are used conventionally to introduce longer quotations which cannot be fit easily into the grammar of the main prose:
- In sonnet 116, Shakespeare said: Love is not love/ Which alters when it alteration finds...
As you can see in the example above, a colon is also used to introduce a separate sub-paragraph - note that in essays, many longer quotations will be given a sub-paragraph of their own. A colon also introduces a list. To recap, so far we have illustrated three things which a colon can be used to introduce: quotations, sub-paragraphs and lists.
In all the above examples, the two sections separated by a colon are grammatically distinct and complete regardless of the other. It would be grammatically correct to separate them with a full-stop, but the decision to use a colon is made to indicate the connection between the two. This can cause some confusion. Look at the following:
- One of Shakespeare's most famous declarations about love is: Love is not love/ Which alters when it alteration finds;
- A colon should be used to introduce: a quotation, a sub-paragraph or a list.
In these examples, the colon is used incorrectly because the two clauses either side of the colon are not grammatically complete.
A colon can have a number of other rhetorical effects, mostly by giving emphasis to explanations and examples. For example:
- A colon does something useful for the writer: it introduces a pause which can be used for emphasis;
- Punctuation can often cause confusion: an example is the correct use of colon.
Be careful if using colons for emphasis to make sure that it’s appropriate, and avoid over-use. Attention also needs to be paid to the use of capital letters after colons. Opinion is divided as to whether a capital letter should be used after a colon or not.
In general, most people agree that a capital letter is needed if a colon is followed by a quotation or by more than one sentence. Whether you use one in other cases or not, the main thing is to make sure you are consistent throughout the whole of your essay.