Colons punctuate sentences in several ways. For the most part, whatever appears after the colon will explain, define, emphasize, name, complete, or expand on whatever appears before the colon. To a certain extent, you could replace the colon with the word “namely.”
Sometimes only a single word appears after the colon:
Note that the word following the colon identifies or labels the “distinct smell.” The only restriction is that an independent clause must come before the colon.
Colons introduce a list:
In this example, the list of items defines “everything we need for the night” or specifically names the items needed for the night. It is important to note that colons can only introduce a list after an independent clause. You would not use a colon to introduce a list that is part of a preposition, such as the list in the following sentence:
While you’re visiting we will go hiking, biking, and canoeing.
In this same way, colons can introduce a quotation as along as an independent clause appears before it.
Colons can join two closely related independent clauses:
Again, the clause that appears after the colon names or explains the choice that the subject, George, has made.
Colons also have some less common uses: