Punctuation Marks in English Langauge : the COLON mark

The Colon except in conventional uses is practically obsolete.

1. It is generally put at the end of a sentence introducing a long quotation: "The cheers having subsided, Mr. Bryan spoke as follows:"

2. It is placed before an explanation or illustration of the subject under consideration: "This is the meaning of the term:"

3. A direct quotation formally introduced is generally preceded by a colon: "The great orator made this funny remark:"

4. The colon is often used in the title of books when the secondary or subtitle is in apposition to the leading one and when the conjunction or is omitted: "Acoustics: the Science of Sound."

5. It is used after the salutation in the beginning of letters: "Sir: My dear Sir: Gentlemen: Dear Mr. Jones:" etc. In this connection a dash very often follows the colon.

6. It is sometimes used to introduce details of a group of things already referred to in the mass: "The boy's excuses for being late were: firstly, he did not know the time, secondly, he was sent on an errand, thirdly, he tripped on a rock and fell by the wayside."