Grammar Girl here.

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Today's topic is semicolons.

I get questions about semicolons a lot, so it's time to clear up some confusion.

Semicolons separate things. Most commonly, they separate two main clauses that are closely related to each other but that could stand on their own as sentences if you wanted them to.

Here's an example: "It was below zero; Squiggly wondered if he would freeze to death." The two parts of that long sentence that are separated by a semicolon could be sentences on their own if you put a period between them: It was below zero. Squiggly wondered if he would freeze to death.

One reason you might choose to use a semicolon instead of a period is if you wanted to add variety to your sentence structure, for example, if you thought you had too many short, choppy sentences in a row. But when you use a semicolon, the main clauses should be closely related to each other. You wouldn't write, “It was below zero; Squiggly had pizza for dinner,” because those two main clauses have nothing to do with each other. In fact, the other reason to use a semicolon instead of a period is if you want to draw attention to the relationship between the two clauses.

People often ask me what the difference is between a semicolon and a colon, and there are a couple of differences. First, the purpose of a colon is to introduce or define something. For example, you could write, “Squiggly checked the temperature: it was -20 degrees.” I'll admit that these differences can be subtle, but I would use a colon in that sentence instead of a semicolon because the second clause (the temperature) strongly relates back to the first clause (Squiggly checking the temperature).

The second difference between a colon and a semicolon is that when you are joining things, you use a  semicolon to join things of equal weight, whereas you can use a colon to join things of equal or unequal weight. For example, you can use either a semicolon or a colon to join two main clauses, but you can only use a colon to join a main clause with a noun. Here's an example: "Squiggly missed only one friend: aardvark." You couldn't use a semicolon in that sentence because the two parts are unequal.

One way that I remember this is to think of the different elements as railroad cars. (In my imagination it's the train in the Schoolhouse Rock cartoon “Conjunction Junction.”) I only use a semicolon if I'm joining two equal “boxcars.” If I'm joining two unequal elements, like a boxcar and a caboose, then I know that I can't use a semicolon, and I consider whether a colon makes sense. So equal sentence boxcars get a semicolon, and unequal sentence boxcars and cabooses often get a colon (or a dash).

Also, one important thing to remember is that you never use semicolons with coordinating conjunctions such as and, or, and but when you're joining two main clauses. Instead, if you're joining two main clauses with a coordinating conjunction, you use a comma. For example, "It was zero, and Squiggly wondered if he would freeze to death.”

I don't want to confuse you, but there is one situation where you use semicolons with coordinating conjunctions, and that's when you are writing a list of items and commas just don't do the job of separating them all. Here's an example: "This week's book winners are Herbie in Milligan College,  Tennessee; Matt in Irvine, California; and Jan in Oklahoma City, Oklahoma." Those are the real winners in this week's special Scott Sigler book giveaway, and they've each won a copy of his novel Earthcore, but the list also provides a great example of using semicolons in a list. Because each item in the list requires a comma to separate the city from the state, you have to use a semicolon to separate the items themselves.

Finally, you use a semicolon when you use a conjunctive adverb to join two main clauses. Conjunctive adverbs are words such as however, therefore, and indeed, and they "usually show cause and effect, sequence, contrast, comparison, or other relationships" (1). For example, “The aardvark is on vacation; therefore, Squiggly has to carry the weight in this episode.” (The comma after the conjunctive adverb is optional.)

Sometimes people seem frustrated because they have to remember to use commas with coordinating conjunctions and semicolons with conjunctive adverbs, so if you can't keep the difference straight in your head, it can help to remember that commas are smaller than semicolons and go with coordinating conjunctions, which are almost always short two- or three-letter words—small punctuation mark, small words. Semicolons are bigger and they go with conjunctive adverbs, which are almost always longer than three letters—bigger punctuation, bigger words. I'll put a list of the two kinds of connectors on the website.

That's all.

For the normal book giveaway, people enter by e-mailing me or posting a message on the blog, but for the next few weeks I'm giving away books from Scott Sigler, the famous podcasting novelist, in anticipation of the release of his new science fiction novel called Ancestor, which is coming out on April 1st. I'll be giving away his older novel, Earthcore, until March 15th, when I will give away three copies of Ancestor. Enter this special book giveaway by sending an e-mail to sigler@quickanddirtytips.com before March 15th.

Questions and comments for me, Grammar Girl, go to feedback@quickanddirtytips.com or the voice-mail line at 206-338-GIRL (4475). You can find a full transcript of this podcast at QuickAndDirtyTips.com, where you can also find other great Quick and Dirty Tips podcasts such as Modern Manners, Money Girl, and the Traveling Avatar's Quick and Dirty Tips for a Better Second Life. I just joined Second Life, so I'm finding the Traveling Avatar's tips especially useful right now. My Second Life name is Comma Tripsa, and I usually end up at Podcast Island. So if you see me there, please say hi and don't laugh at me when I bump into walls.

Next week, Mr. Manners will talk about elevator etiquette.

Thanks for listening.

References

1. Wikipedia contributors. "Conjunctive Adverb," Wikipedia, The Free Encyclopedia, en.wikipedia.org/w/index.php?title=Conjunctive_adverb&oldid=108619955 (accessed February 23, 2007).