# Punctuation in mathematical writing.

I am trying to collaborate with a fellow student on a piece of work. Unfortunately we have now reached a creative impasse.

I am under the impression that to include punctuation marks in equations appearing in a body of text is unnecessary, and that punctuation after equations can lead to unclear reading---what if, for example, one is using index notation?

My colleague claims that it does not make it harder to read, and that it is in fact much more satisfying to appreciate the mathematics as part of a broader sentence structure.

Any thoughts to contribute to this debate?

• See tex.stackexchange.com/questions/7542/… if you are using tex – user332714 Jun 3 '16 at 9:49
• Can you please provide a few examples which illustrate this? It's a little hard to refer to your debate otherwise. – barak manos Jun 3 '16 at 10:03
• Rich discussion evolved over there. – mykhal Apr 29 '17 at 2:40

Yes, punctuation's okay, see

https://en.wikipedia.org/wiki/Wikipedia:Manual_of_Style/Mathematics#Punctuation_after_formulae

for details. More generally, google $\ \mbox{ mathematics$\ $style$\ $guide }\$ for lots of other info.

And, yes, if you're asking about punctuation, then you've indeed "reached a creative impasse" :)

I would say punctuation SHOULD be a part of the equation. Each equation is a part of a sentence, even if it is a very long equation, and the sentence must end with a punctuation.

In fact, when writing my masters thesis, my supervisor INSISTED on me putting in the punctuation.

I agree with the majority of the answers and upvotes in the tex.SE thread that lastresort linked to in a comment, and the answers and upvotes in the MO thread linked to in one of the answers there. Mathematical expressions and equations are usually embedded in sentences, acting roughly as noun phrases and clauses, respectively, and to me it feels unnatural not to provide them with punctuation just like other sentence components. I very rarely encounter problems of lack of clarity. In displayed equations, the punctuation should be slightly spaced away from the equation; I usually use \;, which is enough to separate the punctuation from anything that it might otherwise be taken to be associated with, and if in special cases you feel that this isn't enough, you can always add more space.

• An additional thin space should be inserted between a subscript and any following punctuation. When no subscript is present, the default spacing is normally sufficient. – John Bentin Jun 3 '16 at 12:21

An equation can be thought of as a complete thought or sentence, so that all puctuation: comma, semi-colon, colon and period would apply in the same way.

• I take your point, but the Question (now over a year old) seems to concern how hard or easy said punctuation makes it to read an equation. Given the brevity of your Answer, perhaps adding a few more words to address that would be an improvement. – hardmath Feb 17 '18 at 2:44