The Colon (punctuation) reference article from the English Wikipedia on 24-Apr-2004
(provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Colon (punctuation)

People like you are child sponsors
Punctuation marks
; apostrophe ('), () ; brackets ((, )), ([, ]), ({, }), (, ) ; colon (:) ; comma (,) ; dash (), (), (), () ; ellipsis (...) ; exclamation marks (!, ¡) ; full stop (.) ; hyphen (-), () ; interpunct (·) ; interrobang () ; question marks (?, ¿) ; quotation marks ('), (, ), ('), (,), ;     (, ), («, »), (, ), (, ) ; semicolon (;) ; slash (/) ; space ( )

A colon is a punctuation mark, with one dot above another, like this: ":".

Colons are commonly used to introduce lists, or to connect a broad idea with a specific example: two related sentences can be separated by colons instead of periods. A colon can only be used if the clause preceding the colon is independent.

Table of contents
1 Examples
2 Mathematics
3 Linguistics
4 Computer representation
5 Other meanings

Examples

The United Kingdom comprises four countries: England, Wales, Scotland and Northern Ireland.

Speech is silver: silence is golden.

She had not eaten since breakfast: she'd worked through her lunch break.

Also use the colon...

After the salutation of a business letter.
In the heading of a business memo.
Between the hour and the minutes when telling time.
Between chapter and verse in the Bible, between volume and number in publications, and between title and subtitle.

Mathematics

The colon is also used in mathematics to indicate ratio and is also the standard sign for division in most non-English-speaking countries.
Unicode provides ratio U+2236 (∶) for such matermatical usage if the distinction is required.

Linguistics

A special triangular colon symbol is used in IPA to indicate a preceding long vowel. It is available in Unicode as Modifier letter triangular colon Unicode U+02D0 (ː). A regular colon is often used as a fallback when this character is not available.

Computer representation

In computer programming, the colon corresponds to Unicode and ASCII character 58, or 0x003A.

Other meanings

Colon (anatomy)