To separate a dependent and an independent clause
You should not make such statements; although they are correct.
To separate an appositive phrase or clause from a sentence
His immediate aim in life is centered around two things; becoming an engineer and learning to fly an airplane.
To precede an explanation or summary of the first clause
Although the sentence below is correctly punctuated, the use of the semicolon provides a miscue, suggesting that the second clause is merely an extension, not an explanation, of the first clause. The colon provides a better cue.
The first week of camping was wonderful; we lived in the cabins instead of tents.
The first week of camping was wonderful: we lived in cabins instead of tents.
To substitute for a comma
My roommate also likes sports; particularly football, basketball, and baseball.
To set off other types of phrases or clauses from a sentence
Being of a cynical mind; I should ask for a recount of the ballots.
The next meeting of the club has been postponed two weeks; inasmuch as both the president and vice president are out of town.
Note:The semicolon is not a terminal mark of punctuation; therefore, it should not be followed by a capital letter unless the first word in the second clause ordinarily requires capitalization.
The colon gives the reader a different cue from the semicolon--it tells the reader to look ahead and directs his attention to what follows.
To introduce a list (One item may constitute a list.)
To introduce a list preceded by as follows or the following
To separate two independent clauses, especially when the second clause is a summary or explanation of the first one
To introduce a word or word group which is a restatement, explanation, or summary of the first sentence
To introduce a formal appositive
To separate the introductory words from a quotation which follows, if the quotation is formal, long, or paragraphed separately
The colon should be used only after statements which are grammatically complete.
After a linking verb even though the verb precedes a list
The high school I attended was: old, centrally located, and small.
After a preposition even though it may precede a list
The University Theater will present the 1984 Playwright's Repertory Festival, featuring rotating performances of: Major Barbara, You Never Can Tell, and Heartbreak House.
Interchangeably with the dash
Mathematics, German, English: These gave me the greatest difficulty of all my studies.
Information preceding the colon should be a complete sentence regardless of the explanatory information following the clause.
Before the word/words for example, namely, that is, or for instance even though these words may be introducing a list
We agreed to the plan: namely, to give him a surprise party.
There are a number of well-known African-American female writers: for example, Nikki Giovanni, Phyllis Wheatley, Alice Walker, Toni Morrison, and Maya Angelou.