Here's another of my grammar articles from the old Suite101 site. For more, see the links under January 2015 on the right-hand side of the blog.
The semi-colon—a period on top of a comma—looks as if it can’t make up its mind. There’s good reason for that: It shows a separation of thought that isn’t quite complete.
Semi-colons and colons are two pieces of punctuation that beginning writers often think of as unnecessary. Why use them, they ask, when a comma or period will serve as well?
In fact, a comma or period can serve for most casual forms of writing. But for academic, business, and professional writing, writers must often demonstrate a greater understanding of the relationship of ideas, hence the need for colons and semi-colons. (In a future post, I’ll deal with colons.)
There are really only two uses for a semi-colon: to join two independent clause and to separate elements in a list.
I. Join Two Independent Clauses
Use semi-colons to join two independent clauses that could stand on their own as complete sentences. A period could, of course, quite easily be used instead; however, the semi-colon demonstrates a closer relationship between the ideas, as the semi-colon did in this sentence and below:
John went to the store. He bought milk.
John went to the store; he bought milk.
Of course, you can also recast the sentence in any number of ways, such as by making the first clause dependent on the second: “When John went to the store, he bought milk.”
However, the semi-colon gives us more than information; it also shows emphasis. The writer calls attention to John's purchase of milk as opposed to, say, beer or lottery tickets.
Semi-colons can also join independent clauses that would sound awkward or wordy if they were joined in another way:
The Smiths sold their house far below market value; rather than turning it into rental property, they chose to get rid of it.
In this example, you could use “because” and a comma instead of a semi-colon. However, doing so would make the sentence wordy. One of the cardinal rules of writing is never use two words when one will do.
II. Separate Elements in a Series
The other major use for semi-colons is to separate items in a series. However, they should only be used this way when the list uses internal punctuation or when needed to clarify the relationship of items in the series:
The following stops are on our itinerary: Kansas City, Missouri; Lawrence, Kansas; Denver, Colorado; Santa Fe, New Mexico; Grants, New Mexico; and Tucson, Arizona.
The semi-colons clarify that there are only six stops on the trip, not twelve.
Semi-Colons Gone Bad
Do not use a semi-colon if one of the two clauses is a dependent clause:
You can save time by going to the store on Oak Street; and it’s cheaper.
Do not use a semi-colon in place of a comma:
For example; they have specials on frozen food this week.
Do not use a semi-colon to introduce a quote:
Racing down the stairs, Mitch shouted; “Leave my car alone!”
Do not use semi-colons with short lists or lists in which the relationships of the items is already clear:
The Beatles consisted of John Lennon; Paul McCartney; George Harrison; and Ringo Starr.
Correct the following passage. (Answer appears at end of article.)
When moving to a new apartment, you must do several things, for example, call the utilities to have your service switched over, notify family, friends, and your employer of your change of address, and make sure you have enough money to cover moving expenses. Also, don’t forget to tell your landlord that you are moving out.
The semi-colon is actually a very useful and easy-to-use punctuation mark. It shows the relationships of ideas and keeps the reader moving forward in a way that a full stop (period) cannot. There are really only two uses for semi-colons—those identified above—and, if you master them, your writing will be better for it.
(Answer: Replace the comma after “things” with a semi-colon. No other semi-colons are needed because the relationship between “family,” “friend,” and “your employer” is already clear.)