Punctuation is the bane of many a student's existence. Where do you put it, and why do you put it there at all? Trying to unravel the mysteries of mechanics can be a pain. So why make the attempt? The answer is this: for your reader. If you punctuate your paper well, your readers can concentrate their effort on understanding your ideas, rather than trying to figure out what your ideas are. An accurately punctuated paper reads much as a well-prepared speech sounds--all the inflection is in the proper place to convey exactly what you intend.

Commas are probably the most difficult pieces of punctuation to use. This is undoubtedly because they are not only one of the most common pieces of punctuation, but they are also used for the widest variety of purposes. They can do the following: form compound sentences; set off introductions, transitional expressions, or mild interjections; list items in a series; separate coordinate adjectives; and help punctuate quotations, addresses, dates, numbers, and titles or degrees (like Ph.D.) to name a few. They also separate "interrupters," or additional and grammatically unnecessary information of some kind, from the rest of a sentence.

Remembering the rules governing comma use is bad enough. What happens when other pieces of punctuation can serve essentially the same purpose? Dashes and parentheses can also be used to set off "interrupters," but commas, dashes, and parentheses--we'll call them the three Weird Sisters--serve subtle but distinctly different purposes.

Weird Sister # 1: Commas
There are a million and one rules governing the use of commas, but we're going to concentrate on the "interrupters" here because that is where situations that call for commas and situations that call for dashes or parentheses can be confused. What exactly is an "interrupter"? Any one of the following:

• Nonrestrictive modifier
• Nonrestrictive appositive
• Parenthetical element

Wait a minute, now we're getting technical! Don't worry, it's not as bad as it sounds. A restrictive modifier defines, or restricts, the noun or pronoun that it modifies (Schiffhorst and Pharr 118). You wouldn't enclose such a modifier in commas because it tells you exactly which member or members of a large group you are talking about. Here's an example:

People who are eighteen or older can vote.

The phrase "who are eighteen" is the restrictive modifier here. You wouldn't put it in commas because then you'd be saying that all people are eighteen and all people can vote. Without the commas, you're restricting the large group of people, not all of whom can vote, to a smaller group-those eighteen and older, who can. When is a modifier nonrestrictive? When you're already talking about something specific and want to give your reader additional information. For example:

My sister, who is eighteen, can vote.

Almost exactly the same phrase has been used, but here we're already talking about someone specific-my sister. The age is additional information about my sister and is not necessary. The sentence could have read "My sister can vote" and it would have still made sense, but the sentence "People can vote" wouldn't necessarily be true. Babies are people, and they can't vote (at least not yet).

Appositives are a little easier. All appositives do is rename a previous noun:

My cat, Luke Skywalker, is friendly and affectionate.

Almost all appositives are nonrestrictive; that is, they redefine something specific and are enclosed in commas. In the example above, all "Luke Skywalker" does is rename what we're already talking about--my cat. Now if I had seventeen cats, I'd not only be a little weird, I'd have to tell you which one we were talking about. In that case,

My cat Luke Skywalker is friendly and affectionate.

would be correct because I'm both redefining the noun "cat" and restricting my sentence to describe one of my seventeen cats.

Parenthetical elements are even easier. They are "words, phrases, or clauses inserted into a sentence to clarify or emphasize a point or to give extra information" (Schiffhorst and Pharr, 121). If you're addressing someone directly, or using words like however and nevertheless, set those things off with commas. Likewise, any information which is not grammatically necessary, but which is interesting or important for your readers to know, should also be enclosed in commas.

Weird Sister #2: Dashes
First of all, a dash is not a hyphen. A hyphen is not a dash. They are two different things. To learn how to use a hyphen, see Darren Crovitz's article "The Missing Link." All you need to know about hyphens here is that it is the key to the right of the zero on the number row of your keyboard. In order to create a dash, hit the hyphen key twice. There are no spaces before, between, or after a dash.

Now, when are dashes used? Like commas, they set off parenthetical elements. Unlike commas, they are extremely emphatic. Use them if you want to indicate an abrupt change in subject matter or tone, as in the following example:

My sweet Aunt Mathilda--who I actually couldn't stand--always used to pinch my cheek and tell me how cute I was.

Without the information that I actually couldn't stand my Aunt Mathilda, the sentence would have a very different tone. If the sentence simply read, "My sweet Aunt Mathilda always used to pinch my cheek and tell me how cute I was," my reader would assume I really thought she was sweet, when actually I was being sarcastic. I could have put that information in commas:

My sweet Aunt Mathilda, who I actually couldn't stand, always used to pinch my cheek and tell me how cute I was.

Punctuating it that way, however, just doesn't emphasize the information the way that I would if I were speaking. The dashes provide the dramatic pause I'm looking for. Dashes can also be used to separate parenthetical elements that already contain commas:

Cleaning the bathroom--which includes the shower, the toilet, the floor, and the sink--is the hardest of all the chores.

The sentence above is easier to understand than the following:

Cleaning the bathroom, which includes the shower, the toilet, the floor, and the sink, is the hardest of all the chores.

The second sentence has so many commas that it could be confusing for your reader, so using dashes is a good choice. Just remember that dashes should be used infrequently or they will lose emphasis and visually clutter your paper. You can't stress everything, and because they draw the reader's eye, that is all your reader will see if you overuse them.

Weird Sister #3: Parentheses
Parentheses also set off--you guessed it--parenthetical material. How do they differ from commas and dashes? As we've seen, commas relate material to the rest of the sentence, and dashes emphasize (Schiffhorst and Pharr 140). Parentheses are basically the opposite of dashes: they de-emphasize material and encourage your eye to skip over it. Parenthetical citations, like the one I used in this paragraph, are a great example. The average reader will skip right over it because it's not important (unless you're a Comp I teacher).

Other material can certainly go in parentheses, like definitions or explanations:

Belligerent (from the Latin root bellum) means waging war.

In the example above, all that I wanted the reader needed to know is what belligerent meant; knowing the origin of the word was not as important. Using dashes would have indicated that the origin of the word is more important than the word, and using commas would have made the word and its origin equally important.

Just like overuse of dashes, overuse of parentheses should be avoided. What you want to keep in mind is that by using parentheses, you're sending your reader the message that the information contained in them isn't as important as the rest of the sentence, paragraph, or paper. If the information is important, maybe it would be better to work it into your sentence another way. If the information isn't that important, think about whether you need to include it in your paper at all. Too many parentheses could give your reader the impression that nothing you have to say is important, and you don't want that!

When These Three Shall Meet Again
Well, hopefully not in thunder, lightning, or in rain! But now that you know which Weird Sister is which, you can use the ingredients of the grammatical cauldron to cast a spell that will convey your message clearly to your readers. Just avoid the eye of newt and toe of frog.

Sources: Schiffhorst, Gerald J., and Donald Pharr. The Short Handbook For Writers. 2nd ed. New York: McGraw-Hill, Inc., 1997.