Colon (:)

The colon (:) has primarily three grammatical uses and several non-grammatical uses. The punctuation mark introduces a list. The colon is used to introduce a list of items.

Introducing the colon - English's most feared punctuation

A colon (:) is a punctuation mark comprised of two dots along a vertical line. The colon is used in hours, minutes, subtitles, and at the end of sentences that directly precede block quotes and numbered or bulleted lists.

A colon serves to inform the reader that the sentence preceding it is defined, explained, or elaborated on by the contents that follow. In English texts, anything that comes before a colon is a complete sentence, regardless of whether sentences are formed by the contents that come after.

There's no official rule on the use of capitals on non-proper nouns immediately after a colon; American texts often capitalize after colons, but British texts follow the mark in lowercase.

Rules to follow

Colons are used to divide the numbers that represent hours, minutes, and seconds:

I'm supposed to meet my client at 1:00 PM on Friday.

With a Hail Mary pass, Johnson saved the game at 08:59:59.

Colons are also used for apposition when a subtitle is used to elaborate on a main title, such as with the following movies:

Pirates of The Caribbean: On Stranger Tides

Leprechaun: Back 2 Tha Hood

Lara Croft Tomb Raider: The Cradle Of Life

A colon can also be used before the definition of a subject within a sentence, or vice versa:

I came away badly burned by that evil-eyed scoundrel, but I learned one valuable lesson: always trust your initial instincts about a person.

The Republicans were leading in the polls until the one debate where he committed the gaffe heard round the world: the oops moment.

When an article concerns a list of items, ingredients, or instructions, an introductory paragraph is followed by a colon that precedes the list itself.

Background history on the colon

The word "colon," as it is known in English, derives from the Latin word of the same spelling. In British English, the mark used to be followed with a dash as a way of encouraging momentary pauses, but this usage ultimately fell out of favor. In the Swedish and Finnish languages, the colon is placed inside certain words in a style resembling the possessive use of the apostrophe in English.

In English departments at American universities, the use of colons in essay titles has been a popular literary device. Professors often favor the colon because it builds interest to a title and helps to convey the point of the text within a few select words. Examples include the following:

Secret Understanding: The Idiomatic Breadth Between Maximalism and Minimalism – Here, the first two words that comprise the main title are chosen to arouse curiosity; who or what is having a secret understanding? The words that follow the colon give a more direct hint to the contents of the essay, while elaborating on why the two words preceding the colon—lifted from a song lyric quoted at the end of the essay—were chosen in the first place.

Trumpet Blast: The Global Elephant Wars – Once again, two evocative words that form a curious phrase, but could ultimately be referring to various different topics: jazz, marching bands, sporting events, a saxophonist's bio, etc. After the colon, four words appear that not only put "Trumpet Blast" into context, but also manage to succinctly convey the subject of the essay.