Using the Colon (:)

 Description:

Punctuation mark used after a statement to introduce further related ideas, such as with a quotation, an explanation, or a series. It is also used in business letters after the salutation, between the hour and minutes of time, in a ratio, and between chapter and verse in biblical reference.

Uses:

1. The colon is most commonly used to introduce a quotation, explanation, or series, which helps further define or support the statement that precedes it. 

• Every year has four seasons: winter, spring, summer, and fall.
• In Act II, Scene 4, King Lear refuses to bend to the crumbling of his world: “You see me here, you gods, a poor old man,/ As full of grief as of age, wretched in both!” (2.4.267-8).
• The basket was full of fruit choices: apples, pears, oranges, bananas, and kiwi.

2. In business letters, the overall style is much more formal than that of a regular letter: “Dear Mr. White:”

3. For time notation, this is what is probably most often seen in our everyday writing, including event calendars, TV schedules, etc.

• The time is now 1:30 p.m.

4. For ratios in mathematical use, a colon signifies the relationship between two similar things, like a fraction or percentage. 

• The ratio of white balls to blue balls was 70/30 or 7:3.

5. For biblical references, a colon helps easily identify the chapter and verse of a passage to help readers follow along or look up later.

• Continuing from yesterday’s lesson, let’s begin with Job 3:7.

Misuse:

Colons may seem to be logical in certain instances, but if not similar to the above examples, the usage is most likely incorrect. For instance, the first definition states that a comma is used to introduce a quotation, explanation, or series, but it also states that what precedes the colon must be complete. If a period cannot be used where the colon is, then the colon is incorrect. 

• Every year has four seasons.
• Every year has four seasons: winter, spring, summer, and fall.

Another example— 

• The basket was full of fruit choices: apples, pears, oranges, bananas, and kiwi. (correct)
• The basket of fruit included: apples, pears, oranges, bananas, and kiwi. (incorrect)

In the second example, the sentence begins “The basket of fruit included” and then a colon; but this is not an independent clause that can exist on its own. In this instance, no punctuation is needed:  

• The basket of fruit included apples, pears, oranges, bananas, and kiwi.

Such is the most common misuse of the colon. Also, oftentimes writers use a colon where a semicolon should go instead. If the above rules are kept in mind and maintained however, such errors should be avoided with ease.