Habit reader recently asked about the use of semicolons, colons, and dashes. These punctuation marks can be exceedingly helpful for expressing nuance in your prose. But if you misuse them, bad things can start happening to good people. Nuance is a delicate flower; it wilts in the presence of faulty punctuation. This week’s issue of The Habit is the first of a two-part series on the effective use of these three punctuation marks. We’ll talk about semicolons today and colons and dashes next week.

The semicolon is not an especially flexible punctuation mark. In fact, it only does two things:

1.A semicolon separates items in a series IF at least one item in the series contains a comma.
This is sometimes called the “complex series” use of the semicolon. Normally you would use a comma to separate items in a series: 

This Thanksgiving we will be hosting Charles, Martha, and Consuela.

But if one or more of the items in the list includes a comma, semicolons will clear up any possible confusion caused by the extra comma(s):

This Thanksgiving we will be hosting Charles, our crazy uncle; Martha, our aged neighbor who mows her grass in a bathing suit; and Consuela, our accountant.

The semicolons make it clear that we are talking about three guests, each of whom is renamed with an appositive, rather than six guests. This use of the semicolon can be very helpful, but I don’t know when was the last time I used it. Much more important is the second use of the semicolon.


2.A semicolon joins two independent clauses into a compound sentence.
An independent clause is simply a clause (that is, a string of words containing a subject and a verb) that can stand on its own as a sentence. Consider the following two clauses:

She’ll be coming around the mountain
When she comes around the mountain

Any speaker of English can easily see that the first clause can stand alone as a sentence and the second clause can’t. I won’t get any deeper into those technicalities. (If you’re interested,this post goes a little deeper into independent and dependent clauses).

Except for the “complex series” use of the semicolon, you MUST have an independent clause before and after any semicolon you use. 

This Thanksgiving we are hosting Charles, Martha, and Consuela; it is going to be an adventure.

John Barber thinks he can whip me in a fistfight; it’s not going to happen.

When you connect two independent clauses with a semicolon, as in the two examples above, you have created a compound sentence. The other way to create a compound sentence is to join those independent clauses with a comma and a coordinating conjunction (you may have learned your coordinating conjunctions with the FANBOYS mnemonic:For,And,Nor,But,Or,Yet,So). So then, you could say

This Thanksgiving we are hosting Charles, Martha, and Consuela, so it is going to be an adventure.


John Barber thinks he can whip me in a fistfight, but it’s not going to happen.

We have the same independent clauses, this time joined with a comma and a coordinating conjunction. From a strictly grammatical perspective, one way of connecting these clauses is as correct as the other. How does one decide whether to use the semicolon or the comma and coordinating conjunction? To some extent this is just a matter of style. Some people use more semicolons than others. 

In the examples above, I would use the semicolons; the semicolons allow the reader to do a little of the work–to make some of the connections herself. You should never ask the reader to do work that is your to do, but giving the reader just a little something to work on can keep her mind engaged. The coordinating conjunctions–“so” in the first example and “but” in the second–feel a little like spoon-feeding to me. 

The astute reader will have already noticed that any time you insert a semicolon (again, setting aside the “complex series” use of the semicolon), you could also have inserted a period.

This Thanksgiving we are hosting Charles, Martha, and Consuela. It is going to be an adventure.

John Barber thinks he can whip me in a fistfight. It’s not going to happen.

The semicolon joins independent clauses; the usual end-punctuation for an independent clause is a period. This is an exceedingly helpful thing to remember: if a period wouldn’t work between two clauses, a semicolon won’t work there either.

So why do you even need semicolons, if you could just as easily use periods or conjunctions to join independent clauses? It comes down to nuance. A period between two independent clauses doesn’t make any comment on the relationship between those clauses. A semicolon, on the other hand, signals to your reader that two clauses are so closely related that they really constitute one compound sentence. 

If a period makes no comment on the relationship between two clauses, a conjunction makes an explicit comment. The semicolon gives you the opportunity to be less explicit.

I like the semicolon a lot. In fact, I have to restrain myself from using too many. In my mind, almost all of my sentences are closely-enough related to be joined by a semicolon rather than a period; that’s why I put them next to one another. However, if you over-use the semicolon–that is, if you use more than two or three per page of prose–it will lose its effect and just seem like a verbal tic.

Next week we’ll tackle colons and dashes. These two punctuation marks–especially dashes–are slightly more flexible in their use. But the semicolon is blessedly inflexible. You can use it to join items in a complex series, or you can use it to join independent clauses. And in that second, much more common use, just remember that if a period wouldn’t work, a semicolon won’t work either. If you’re doing anything else with a semicolon, you are introducing a punctuation error that will blow up whatever nuance you were hoping to gain.

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