Someone asked me when to use a semicolon or a colon to separate two sentences. Here’s the difference.
A semicolon separates closely related sentences.
Example: My grandmother seldom goes to bed this early; she’s afraid she’ll miss out on something.
If you notice in this example, the second sentence explains or amplifies the idea of the first–it is like saying that the second sentence completes the idea of the first.
Capital Community College’s Guide to Grammar and Writing explains, thus:
The semicolon allows the writer to imply a relationship between nicely balanced ideas without actually stating that relationship. (Instead of saying because my grandmother is afraid she’ll miss out on something, we have implied the because. Thus the reader is involved in the development of an idea—a clever, subliminal way of engaging the reader’s attention.)
What the semicolon does is create the relationship between two sentences. Let’s consider the following two sentences using a period:
Mary drives a Mercedes. Joanne drives a Chevrolet.
When we use the period in the above sentences, we create two discrete, distinct sentences. We do not see the relationship between them. What if we use a semicolon?
Mary drives a Mercedes; Joanne drives a Chevrolet.
You can see that there is a relationship of CONTRAST between the two sentences. It is like saying Mary drives a Mercedes, BUT Joanne drives a Chevrolet. Or Mary drives a Mercedes, WHILE Joanne drives a Chevrolet.
The University of Victoria explains:
When we use a semi-colon, it is often because we want to make the reader think about the relationship for herself. This is useful in many situations, such as when writing cautiously, ironically, or humorously.
A colon often introduces a list or explanation. The equation is SENTENCE + COLON + LIST/EXPLANATION. The colon may be used to emphasize a word, phrase, clause, or sentence which explains, impacts or defines the main clause.
Example of introducing a list
We need three items to complete our party: A bucket of ice, great wine, and spinach dip for the chips.
Examples of introducing an explanation
Yesterday, a revolutionary new plan was unveiled to “solve” one of Xavier’s most frustrating problems: parking.
Let us not forget this point: Appositive phrases have an entirely different function than participial phrases and must not be regarded as dangling modifiers.
I’ll tell you what I’m going to do: I’m going to quit!
The clause that comes before the colon must be a complete sentence. But the list or explanation that comes after the colon need not be a sentence.
The Guide to Grammar and Writing discusses that a colon is like a door or a gate, inviting us to go on. A colon tells us that there is either an explanation or an enumeration. Because of the sentence that comes before the colon, we nearly always have a sense of what is going to follow the colon.
Here are some examples of using the colon:
There is only one thing left to do now: confess while you still have time.
The charter review committee now includes the following people:
- the mayor
- the chief of police
- the fire chief
- the chair of the town council
Other sources: Xavier Writing Center