An important step in developing a mature writing style is the proper use of the full repertoire of punctuation marks. Too many student essays contain nothing more than the standard mix of commas and periods (and even these often misused). How much better these essays would be if they employed also the power of the semi-colon, the colon, the dash, the parentheses, and even the exclamation mark!
First, a brief refresher on commas and periods. Commas join independent clauses to dependent ones, and separate items in a list. Make sure to include the comma after every item in the list, including the one before the "and"
I have been to Hawaii, Alaska, and Texas.
Periods end complete sentences. If the sentence is incomplete, but ends in a period anyways, it is a sentence fragment. If two complete sentences are written as one sentence without a period, it is a run-on sentence. Try to avoid both of these. Sentence fragments beginning with "and" or "but" can be acceptable, if they are done deliberately, for emphasis.
He reached out to take the jeweled scarab. But then he remembered the curse.
If you are not sure whether or not this sort of construction will work for you, avoid it. A little loss of emphasis is better than writing something that looks like a basic grammar mistake.
Now, for the good stuff:
Colons introduce quotations, lists, examples, or explanations:
As T.S. Eliot once wrote: "The last temptation is the greatest treason: to do the right deed for the wrong reason."
He soon regretted his choice of words: the bouncer was obviously getting angry, and looked strong enough to rip him in half without breaking a sweat.
The semi-colon can be used in place of a period to connect two closely related sentences. Note that the semi-colon is used to connect two complete sentences:
The manager decided to promote Lawrence; the decision soon had startling repercussions.
The semi-colon can also be used in place of comma to connect items in a list when those items themselves include commas, in order to avoid confusion:
The attacks occurred in Little Town, Kentucky, on January 7th, 1973; Jamestown, Virginia, on April 2nd, 1987; and Houston, Texas, on November 13th, 1981.
Dashes can also replace commas, and are normally used to create a more informal feel to the writing, or to set off items a bit more strongly than commas do. They also tend to slow down the flow of the essay less than commas do:
He pulled his punches - he didn't want to do permanent damage – but he knew he had to make the fight look good if the gang was to take him seriously.
Parenthesis can be an excellent way of going off on a tangent without weakening your essay (though you should use them with care, because if you let your parenthetical comments get too long, your reader might lose track of your original point).
Exclamation marks are so overused to indicate emphasis that many writing guides recommend avoiding them altogether. However, there is nothing at all wrong with using them to end actual exclamations, as I did at the start of this article
How much better these essays would be if they employed also the power of the semi-colon, the colon, the dash, the parentheses, and even the exclamation mark!
These punctuation marks are not as common as the comma or period, nor should they be. However, any essay of length that has none of these punctuation marks in it is likely weaker than it could be. The use of these punctuation marks is one way of varying sentence structure to maintain reader interest. It also allows the writer to convey more subtle shades of meaning in his writing by indicating nuances in the connections between his ideas.