In my field of study, I often see statements such as, "... such that, for every person, there were two chairs."

I'm wondering if there should be a comma after "such that"? If so, what are the rules of punctuation that allow and/or necessitate this?

I would greatly appreciate it if someone could please take the time to clarify this point.


The entire context would be similar to the following:

If a, b, and c are real numbers with a < 0, then there is a real number y such that(,) for every real number x, ax^2 + bx + c ≤ y.

  • As far as I know "such…that…" is a correlative conjunction used to give the reason. Will you present the whole sentence and the context, please?
    – Victor B.
    Commented Feb 3, 2017 at 11:59
  • @Rompey Done. I hope that is understandable. Commented Feb 3, 2017 at 12:00
  • If I got it right, "such as" here establishes a circumstance from which the following statement is consequential. Besides its usage in mathematics, I couldn't find any grammar resource where it was presented. Yet, you may want to see how it is punctuated in maths books, for example here.
    – Victor B.
    Commented Feb 3, 2017 at 12:34
  • @Rompey I have seen it punctuated both with and without the comma in mathematics literature. I was wondering what was the correct or most correct way to punctuate it, according to the rules of English punctuation. Commented Feb 3, 2017 at 12:37
  • If Google Books search is anything to go by, it seems that most authors of mathematics textbooks have NOT used a comma (... such that for every person ...). Commented Feb 6, 2017 at 4:55

2 Answers 2


I'm American and I can tell you that it's not dialectal. What you are really saying is "such that there were two chairs" with the parenthetical "for every person." So there are two correct ways to write it:

  1. ...such that for every person there were two chairs.
  2. ...such that, for every person, there were two chairs.

The former is more likely if it's a short sentence and the commas don't make the sentence difficult to decipher or ambiguous. (It may also be more common in America). The latter is more likely if the sentence is long or ambiguous without the commas. In speech you may well hear *"such that for every person, there were two chairs" but it is not correct to write it that way. You can choose to put a comma on both sides of a parenthetical or neither but you can't have one comma.


Yes, a comma goes there.

However, being raised on British English, I cannot speak for other geographic varieties. In American English commas tend to be dropped in places, which would explain the inconsistencies you have observed.

All in all, I think it depends on which English you are learning.

  • Thanks for the response. I use British English too. What is the principle that indicates we use a comma there? Commented Feb 6, 2017 at 17:46
  • 1
    I believe it's the rule of parenthetical phrases. Commented Feb 6, 2017 at 19:49

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