Center For Academic Excellence
Writing Center | Colons and Semicolons
One look at a semicolon will tell you what it is: It's something like a comma, and it's something like a period. It is, actually, a strong comma and a weak period.
Here's how it works for you to help you make the meaning of your writing clearer.
1. Use a semicolon when you write a series of phrases or clauses which contain commas within themselves:
On the Oprah Winfrey Show were Tom Gibson, an actor; Bob Dole, a politician; and Bishop Fry, a theologian.
Notice that the semicolons separate the names of the larger units (guests and their roles); commas separate the names from their roles (within the larger unit).
2. Use a semicolon to separate main clauses which are closely related in content:
I am taking a course in algebra; my math skills are not very good.
A house without a cat is not a home; a farm without a cat is a haven for vermin.
[Sometimes, there will be a conjunctive adverb (however, therefore) or a transitional phrase (after all, for example) which serve to further delineate this close relationship.]
Caution: Do not use a semicolon between parts of unequal grammatical rank, such as a clause and a phrase,or a main clause and a subordinate one.
X John left the doctor's office; after he had waited thirty minutes.
X I have a thoroughbred horse; a beautiful one.
A colon is a sort of sign post which says, "Read on!" It is used as a formal introducer to call attention to what follows:
1. It may direct attention to an explanation or summary, a series or list, or a quotation.
I grew up in the fifties: a young woman who felt neither discriminated against or handicapped.
These are the things I want for Christmas: a full eight hours' sleep, a clean house, and a perfectly manicured lawn.
I distinctly heard him say: "The Owl and the Pussy-Cat went to sea / In a beautiful pea-green boat; / They took some honey, and plenty of money / Wrapped up in a five-pound note."
2. A colon may introduce a second main clause when it explains or amplifies the first main clause.
Fishing is more than a sport: it is man's contest against nature.
(Please note that the second clause may or may not begin with a capital letter. This is a matter for judgment. If the second clue is long or detailed, use a capital letter; otherwise, don't!)
3. Use the colon between figures in scriptural and time references, between titles and subtitles, after the salutation of a business letter, and in bibliographical data.
John 3:16 8:30 A.M. Calling: A Song for the Baptized Dear Mr. Jones:
4. Do not use superfluous colons. Be especially careful not to use a colon between a verb and its complement or object, between a preposition and its object, between the parts of an infinitive (to + a verb), or after "such as."