A colon introduces a further thought, one added to throw light on a first. Some writers use a capital letter to start any complete sentence that follows a colon; others prefer a lowercase letter. Whichever you choose, be consistent. A phrase that follows a colon always begins with a lowercase letter.
23a | Use a colon between two main clauses if the second exemplifies, explains, or summarizes the first |
main clause: A group of words that has both a subject and a verb and can stand alone as a complete sentence: My friends play softball.
Like a semicolon, a colon can join two sentences into one. The chief difference is this: a semicolon says merely that two main clauses are related; a colon, like an abbreviation for that is or for example, says that the second clause gives an example or explanation of the point in the first clause.
She tried everything: she scoured the Internet, made dozens of phone calls, wrote e-mails, even consulted a lawyer.
23b | Use a colon to introduce a list or a series |
A colon can introduce a word, a phrase, a series, or a second main clause, sometimes strengthened by as follows or the following.
The dance steps are as follows: forward, back, turn, and glide.
When a colon introduces a series of words or phrases, it often means such as or for instance. A list of examples after a colon need not include and before the last item unless all possible examples have been stated.
On a Saturday night many kinds of people crowd our downtown area: drifters, bored senior citizens, college students out for a good time.
23c | Use a colon to introduce an appositive |
appositive: A word or group of words that adds information by identifying a subject or object in a different way: my dog Rover, Hal’s brother Fred
A colon preceded by a main clause can introduce an appositive.
I have discovered the key to the future: robots.
23d | Use a colon to introduce a long or comma-filled quotation |
Sometimes you can’t conveniently introduce a quoted passage with a comma. Perhaps the quotation is too long or heavily punctuated, or your prefatory remarks demand a longer pause. In either case, use a colon.
God told Adam and Eve: “Be fruitful, and multiply, and replenish the earth, and subdue it.”
23e | Use a colon when convention calls for it |
AFTER A SALUTATION | Dear Professor James: |
BIBLICAL CITATIONS | Job 9:2 [The book, chapter, verse], but Job 9.2 [MLA] |
TITLES: SUBTITLES | Convergences: Essays on Art and Literature |
SOURCE REFERENCES | Welty, Eudora. The Eye of the Story. New York: Random, 1978. |
TIME OF DAY | 2:02 p.m. |
23f | Use a colon only at the end of a main clause |
main clause: A group of words that has both a subject and a verb and can stand alone as a complete sentence: My friends play softball.
In a sentence, a colon always follows a complete sentence, never a phrase. Avoid using a colon between a verb and its object, between a preposition and its object, and before a list introduced by such as.
FAULTY | My mother and father are: Bella and Benjamin. |
REVISED | My mother and father are Bella and Benjamin. |
FAULTY | Many great inventors have changed our lives, such as: Edison, Marconi, and Glutz. |
REVISED | Many great inventors have changed our lives, such as Edison, Marconi, and Glutz. |
REVISED | Many great inventors have changed our lives: Edison, Marconi, Glutz. |