I'm a software developer and occasionally write user documentation and project proposals for my boss. I've been running into a punctuation problem recently that I've been unable to solve. I have a sentence in the form


For example:

If Jack and Jill were going up a hill and Bob were simultaneously driving down the hill, Bob would run over Jill.

I've been rather confused whether there should be a comma before the and. I realize the two subordinating clauses actually share the if, but a part of me still wants to insert a comma like one would do if the and separated two main clauses. Is there any standard (American) punctuation rule that applies in this sort of corner-case? I realize I could rewrite the sentence in a way to avoid this problem, but I'd really like to know what the generally accepted (American) standard for this is.

  • The discomfort may not be due to presence of and but at most the complexity of the clause. "If It's Tuesday, This Must Be Belgium"
    – Kris
    Aug 15, 2014 at 13:30

3 Answers 3


Your inclination to add a comma to the sentence between hill and and is an instance of wanting to use the comma as a marker for an omitted word or idea. In this case the omitted word is if, since the sentence's internal logic amounts to "if X and if Y, then Z." Such an addition can help with clarity in some cases, or it can be superfluous, depending on the complexity of the sentence.

But if you were to add a second if between and and Bob, I doubt that you would be inclined to add a comma before the and as well, since the parallelism between the first if and the second one would already be well established. Here's the sentence in that form:

If Jack and Jill were going up a hill and if Bob were simultaneously driving down the hill, Bob would run over Jill.

The decision about whether to add a comma or to add if or to leave the original sentence as currently written and punctuated is a judgment call. In this particular case, I don't think that any of the three options produces a bad result.


A comma would clarify the two parts of the qualifying clause and so is necessary.


To your readers, punctuation should be an invisible guide through your sentence and should not burden their eyes. Said differently, don't over do it.

Consider the following:

John, please get the plates.

Quickly, please get the plates.

If you want to use both dependent clauses at the beginning of the same sentence, would you write?

Quickly, John, please get the plates.

Of course not.

I do not have a copy of the Chicago Manual of Style with me, but I believe that is where I read the advice to join these dependent clauses together and use one comma at the end.

Quickly John, please get the plates.

If I did not read about this style rule in the CMS, then it is likely I read it in Eats, Shoots & Leaves. Finally, Strunk and White provide some guidance in this area in rules 4 and 5 of The Elements of Style.

  • 1
    Unless his name really is Quickly John, I'd be inclined to write "John, please get the plates quickly." But of course we're speaking of a sentence with subordinate clauses, rather than that example, aren't we; and the OP didn't want to recast the sentence. Jan 10, 2015 at 5:23

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