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When do you use commas and when do you use parentheses to provide more detail about something?

For example:

  • The suspect, Tom Wilson, is now being charged with murder.
  • The suspect (Tom Wilson) is now being charged with murder.
  • John Smith, a member of the jury, agreed with the verdict.
  • John Smith (a member of the jury) agreed with the verdict.
  • The first example, the one about the fox, is the more valid one.
  • The first example (the one about the fox) is the more valid one.

I realize that the first example, the one that uses parentheses, is probably more valid in this case (if anyone has a better example, please include it), but when, if ever, would you favor parentheses?

Update:
I realize that dashes are sometimes used for similar situations, so I'd appreciate information on these as well.

For example:

  • The children—who are wearing shoes—will go on the trip
  • The children, who are wearing shoes, will go on the trip
  • The children (who are wearing shoes) will go on the trip
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3 Answers 3

up vote 11 down vote accepted

(Nitpick: the plural of 'parenthesis' is 'parentheses'.)

Parentheses are used for digressions - things that could be completely removed without affecting the meaning.

Commas and dashes are for setting off clauses that, while not vital to the meaning, serve to provide a fuller picture. Which to use depends partly on the length of the clause—for example, if the clause itself contains a comma, you kind of have to use a dash—and partly on its importance: at least in my perception, a comma-delineated clause is more important to understanding the meaning than a dash-delineated one.

Of your examples, I'd use a comma for these:

  • The suspect, Tom Wilson, is now being charged with murder.
  • John Smith, a member of the jury, agreed with the verdict.

I'm not sure about this one, but I'd lean toward commas:

  • The first example, the one about the fox, is the more valid one.

I'd almost certainly use parentheses for this one, or at best dashes.

  • The children (who are wearing shoes) will go on the trip.
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"The first example - the one about the fox - is the more valid one". –  CJM Nov 23 '10 at 11:45
1  
@CJM: like I said, I'm not sure about that one; for some reason, when the example was still about parentheses, I leaned toward commas. Now that it's about a fox, I might actually prefer dashes, but didn't want to change my answer that much. As you can see, deciding which punctuation is appropriate is rather subjective. –  Marthaª Nov 23 '10 at 14:15

I've always felt like parenthesis should be used to provide details which are not "directly" related to the meaning of the sentence. In other words, what's between parenthesis can be ignored without jeopardizing the meaning.

For your first example (Tom Wilsons), I think it depends more on the context: In the current text, are they more than one suspect? If yes, I think double commas are more appropriate.

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6  
I would say that both "The suspect (Tom Wilson)..." and "The suspect, Tom Wilson,.." imply that there is only one suspect. I think that only "The suspect Tom Wilson...", without any punctuation, can imply that there could be additional suspects. –  RegDwigнt Oct 29 '10 at 12:39
    
hmm, you are probably right. So, you think that there's no difference between parenthesis and double commas in this case? –  Soufiane Hassou Oct 29 '10 at 13:12
    
I think there is, I was merely commenting on your second paragraph rather than the first one. –  RegDwigнt Oct 29 '10 at 13:38
1  
"Suspect Tom Wilson..." even more heavily implies there is potentially more than one suspect –  Claudiu Oct 29 '10 at 17:44
3  
I'll chime in with RegDwight. Commas or parenthesis mean a non-restrictive relative clause---one which provides information about the affected noun, but does not serve to restrict the possible identity; without punctuation, it's a restrictive clause, which restricts the meaning of the noun. The example I learned from: "The children, who are wearing shoes, will go on the trip" versus "The children who are wearing shoes will go on the trip"; the first means that all the children are wearing shoes, and all will go, while the second means that only the children who are wearing shoes will go. –  Henry Oct 30 '10 at 0:59

The suspect, Tom Wilson, ... and The suspect (Tom Wilson) both imply that there is just one suspect. However, I agree with @RegDwight; Using no punctuation implies that there could be more suspects.

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This doesn't really answer the question... I'm not asking whether to use punctuation or not, I'm wondering which punctuation I should use (i.e. parenthesis or commas). –  Senseful Oct 30 '10 at 0:54
    
also, without punctuation, the sentence reads like you're describing Tom Wilson as suspect, rather than a suspect. –  Matt Эллен Feb 3 '11 at 13:52
    
I agree. I don't know the answer, I was just hoping to give you more to think about, hopefully making it easier to come to a conclusion. I'm sorry I couldn't be of more help. :) –  user461 Apr 11 '11 at 5:53

protected by tchrist Jul 9 at 20:35

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