I always find myself writing sentences that contain clauses within clauses, and I can never decide what the right way to punctuate this is. I'm not specifying what kinds of clauses because they could technically be several different kinds.

So here's an example:

I drove my little brother, Billy—the youngest of us, to the store.

This sentence contains two appositives—one inside the other. Firstly, I know appositives are usually set inside commas, but I feel like nesting them calls for using multiple kinds of punctuation marks. Secondly, is this even the correct way to punctuate this sentence? I feel like it could also be

I drove my little brother, Billy—the youngest of us—to the store.

This might not be correct because now the sentence is broken up by just one comma which creates two incomplete sentences. If so, why is it not correct to say the first example is broken up by the lone em dash?

Edit for clarification:
I'm pretty much asking if I can use the comma and em dash interchangeably here, and if so, which is better?

  • 1
    I think it's your comma after brother that's causing the confusion. The element between em-dashes (or commas, it's just a stylistic choice in your example) is parenthetical. Which means you should be able to remove both it and the delimiters without affecting the grammaticality of what remains. May 13, 2015 at 20:15
  • @FumbleFingers So you're saying that creating an appositive out of Billy isn't necessary?
    – Adam
    May 13, 2015 at 20:28
  • I've no idea what an appositive is, and I don't feel inclined to look it up right now either. What I'm saying is if you remove your parenthetical element (an easy word, assuming you know what parentheses are), it should be pretty obvious you don't want a comma at all. May 13, 2015 at 20:40
  • 1
    ...on second thoughts, I was wrong when I said it was just a stylistic choice whether to use commas, em-dashes, or actual parentheses for parenthetical text. I suspect you're effectively trying to nest one parenthetical element inside another. The convention is that you use em-dashes if the parenthical element itself includes commas, so you might consider I drove my little brother—Billy, the youngest of us—to the store. In principle the youngest of us is a parenthetical addition to Billy, but it would be excessive to try to add a comma after it before the final em-dash. May 13, 2015 at 20:46
  • @FumbleFingers I see what you're saying. Em dashes on the outside does look better and seem more natural than with commas.
    – Adam
    May 13, 2015 at 20:50

1 Answer 1


As @FumbleFingers points out, part of the issue with your first example is the asymmetry of your delimiters. "The youngest of us" is the subordinate phrase that should be removable while leaving the sentence intact. That being the case, you should use the same delimiter either side.

Do remember that, unlike some languages such as German, English does not have hard and fast rules about the placement of commas in every possible situation. From a pragmatic stance, they are there to increase readability. In your example, I would contend that excessive punctuation is making the sentence harder to read and understand: I would simply opt for:

I drove my brother Billy, the youngest of us, to the store.

Your question still stands, though, for longer or more complex sentences. At this point, a "hierarchy of punctuation" is a useful concept. A well-accepted example of this is if you are constructing a list of complex items, each of which contains commas. You maintain commas within list items, and use semicolons as delimiters:

I keep only three things on my desk: a pen, as I can't stand typing; a photo of my son, who now lives in Australia and whom I haven't seen in years; and a seashell from the beach where I met my wife.

In the same way, you can use emdashes as your "outer commas" in a clause, and your commas for the inner ones.

I have always held that emdashes are more emphatic than commas - others seem to agree: http://www.thepunctuationguide.com/em-dash.html

In conclusion, though, don't overuse your delimiters: more often than not, you can make do with fewer; if not, do also try looking for a more elegant way of constructing your sentence.


Not the answer you're looking for? Browse other questions tagged or ask your own question.