# Does inserting a comma change what is modified?

My question pertains to the usage of comma after a list of clauses of the form "X, Y, and Z (,) to/in order to <do something>"

Example:

Apply Equation 1, use Lemma 2, and exploit Theorem 3(,) to prove the finiteness of the result.

Is the comma necessary or not:

1. if Theorem 3 alone is enough to prove the finiteness
2. The three actions "Apply Equation 1, use Lemma 2, and exploit Theorem 3" prove the finiteness.

I'm tempted to add a comma in case 2. above to avoid potential ambiguity with the first case.

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I've edited this question, please feel free to re-edit or revert it if I've misunderstood you. – Mr. Shiny and New 安宇 Nov 9 '12 at 18:28
@Mr.ShinyandNew安宇: excellent, thanks! – r.ductor Nov 9 '12 at 18:32
@r.ductor, the "standard" way of saying this might be "using eq. 1, lemma 2 and thm. 3, we prove the finiteness of the result" I am assuming that you are talking about math here. – picakhu Nov 9 '12 at 23:10

Apply Equation 1, use Lemma 2, and exploit Theorem 3, to prove the finiteness of the result.

In this case the whole list seems to "prove the finiteness of the result".

Apply Equation 1, use Lemma 2, and exploit Theorem 3 to prove the finiteness of the result.

In this case I'd say that it is ambiguous, but can you expect your reader to understand how Theorem 3 does or does not by itself prove the finiteness of the result? If the reader should be able to understand that (and you're sure), then the context resolves the ambiguity. If not, then you should try to reword it.

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Yeah, without the comma rewording is in order: even if the reader can figure it out, it will still be awkward. – Cerberus Nov 9 '12 at 18:29
Simply including or excluding the comma does not really eliminate the ambiguity. If in the full context the meaning would not be clear to the reader, I'd add some more words. – Jay Nov 9 '12 at 21:24

I agree with Mr. Shiny and New 安宇, but I would add the caveat that even though his reading of the version with comma is formally correct, it does not escape the Fundamental Law that "Anything which can be misunderstood will be".

I would suggest moving the final clause to make your meaning unambiguous. If all three operations are required for the proof, then:

To prove the finiteness of the result, apply Equation 1, use Lemma 2, and exploit Theorem 3.

If only the last term is required:

Apply Equation 1, use Lemma 2, and, to prove the finiteness of the result, exploit Theorem 3.

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@Mr. Shiny and New 安宇 and @StoneyB: thanks for your valuable advices.

@StoneyB:

In my real case the three operations are required, and "the finiteness of the result" is a large equation (in a different line). In this case, I think it would be would better to show the resulting equation after listing the operations needed to prove it. To fulfill your Fundamental Law, maybe I should write something like:

Apply Equation 1, use Lemma 2, and exploit Theorem 3; proceeding in this way, prove the finiteness of the result.

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