Punctuation marks are a convention of writing that ensure the clarity of written language for readers and writers. There are eight rules for using colons as punctuation marks in written American English:
- Introduce lists
- Introduce appositives
- Introduce quotations
- Introduce elaborations and emphasizations
- Introduce rules and principles
- In business salutations
- In time notations
- In Bible references
The following sections explain and provide examples of the punctuation rules for colons in written English.
- We sent copies of the report to our regional offices: the north-central office in Garden City, the south-east office in Mobile, and the south-west office in Santa Monica.
- The review committee now includes the following people: the mayor, the chief of police, the fire chief, the chair of the town council, and the city lawyer.
- I need you to pick up a few groceries from the store before you come home: organic eggs, fresh cream, and natural cane sugar.
Do not use a colon to introduce a list that is part of the grammatical structure of the sentence.
Use a colon to introduce an appositive that is not part of the grammatical structure of the sentence. For example:
- The detective has discovered who committed the crime: the laundry mat clerk.
- The committee appointed the best person to the job: me!
- My husband is watching his favorite type of television show: a baseball game.
Do not use a colon to introduce an appositive that is part of the grammatical structure of the sentence.
Use a colon to introduce a quotation including a block quotation that is not part of the grammatical structure of the sentence. For example:
- Martin Luther King, Jr. has inspired many people with just four words of his famous speech: “I have a dream…”
- Alex grabbed the microphone: “Your honor, I object!”
- George Jean Nathan once said: “A man reserves his true and deepest love not for the species of woman in whose company he finds himself electrified and enkindled, but for that one in whose company he may feel tenderly drowsy.”
Do not use a colon to introduce a quotation that is part of the grammatical structure of the sentence.
Elaborations and Emphasizations
Use a colon to introduce an elaboration that provides additional information about the initial sentence or to join two sentences together in which the second sentence emphasizes the first sentence. The first letter of the elaboration or emphasization should be lowercase except for proper nouns. For example:
- The weather was terrible last night: we had sixteen inches of snow in four hours.
- The mall is packed this time of year: Christmas shoppers are crowding into every store.
- All of the crops are destroyed: a tornado wiped out every field.
Rules and Principles
Use a colon to introduce a rule or principle. The first letter of the rule or principle should be uppercase. For example:
- Scientists must consider Newton’s third law of motion: To every action there is an equal and opposite reaction.
- The man learned a valuable lesson: Never argue with your wife.
- The sixth commandment is very clear: You shall not kill.
Use a colon at the end of the salutation of a business letter. For example:
- To Whom It May Concern:
- Dear Sir or Madam:
- Dear Professor Bailey:
Use a colon to separate the hours from the minutes in time notations. For example:
Use a colon to separate chapters and verses in Bible references. For example:
- John 3:16
- Ephesians 2:8
- Genesis 1:1
Punctuation is a convention of writing that helps readers and writers more clearly understand writing by ensuring the clarity of written language. Colons perform eight basic functions in written American English: introduce lists, introduce appositives, introduce quotations, introduce elaborations and emphasizations, introduce rules and principles, in business salutations, in time notations, and in Bible references.
Faigley, Lester. 2003. The Brief Penguin Handbook. New York: Pearson Longman.
Gibaldi, Joseph. 2003. MLA Handbook for Writers of Research Papers. 6th ed. New York: The Modern Language Association of America.