A colon (:) is a formal mark of punctuation. It has two functions only: to introduce and to separate. As a mark of introduction, the colon introduces formal quotations, restatements (पुन:कथन) or clarifying examples, and lists of enumerations. This construction gives more emphasis to these items than alternative sentence structures. As a mark of separation, the colon separates the salutation in a formal letter from the main body of the letter, titles from subtitles, the hours from minutes,etc.

Rule 1:

A colon is used to call attention to a formal quotation. Example:

Franklin D. Roosevelt said: “We have nothing to fear but fear itself.”

NOTE: Do not use a colon to introduce a maxim, a proverb, or a quotation of a single sentence in ordinary dialogue. Example:

  • The saying is, “A stitch in time saves nine.”
  • John said, “Let’s go to the movies.”
Rule 2:

The colon may take the place of expression as in effect, in other words, and namely to introduce new statements, restatements, and clarifying examples. For example:

Readers are of two sorts: one who carefully goes through the book, and the other who as carefully lets the book go through him.-Douglas Jerrold

Rule 3:

The colon is used to introduce formal lists and enumerations. For example:

  • I have come to the following conclusions:
  • Please forward the items listed:
  • Mix the ingredients as follows:

NOTE: Do not use a colon to introduce a list if the sentence does not have an introductory word or phrase to complete it.

Its wrong to write as: The crash injured: Bill, Tom, and David.

Right implementation is: The crash injured three students: Bill, Tom, and David.

Rule 4:

The colon is used in reference to time to separate hours from minutes. For example:

  • 10 : 15 A.M. (US)
  • 10 : 15 a.m. (British)
  • 6 : 50 P.M. (US)
  • 6 : 50 p.m. (British)
Rule 5:

The colon is used to separate a subtitle from a main title. For example:

  • Wheat : The Staff of Life
  • My Father : A member of Mark Twain
Rule 6:

The colon is used to separate verse from chapter in the Bible. For example:

The Song of Solomon 2 : 1

Rule 7:

The colon is used for the following the salutation in a formal business letter. For example:

  • Dear Ms. James :
  • Dear Sir :
  • Gentlemen :
Rule 8:

When the colon appears together with closing quotation marks, the colon always follows the quotation marks. For example:

The teacher said, “Please answer the following questions”:

Rule 9:

The colon always follows a closing parenthesis such as:

The librarian recommended the following books (all by Maugham) :

Rule 10:

The colon commonly used to be joined with the dash. This is no longer accepted usage:

  • Wrong statement: We must follow these rules:–
  • Right statement: We must follow these rules :
Rule 11:

Before direct speech and quotation colon is used. For example:

  • He said : “I will do it.”
  • Shakespeare said : “Sweet are the uses of adversity.”
Rule 12:

Colon is also used in dialogue before the name of the speaker. For example:

  • Teacher: What are you doing ?
  • Ram: Sir, I am doing my lessons.
Rule 13:

Colon is also implemented after a word definition or description are to be given. For example:

  • Noun : A noun is a naming word.
  • Albatross : A large white sea-bird with long wings.