14
$\begingroup$

The Latex command \ldots is often used to denote "and so forth". For instance,

$$ \pi \approx 3.1415\ldots $$

When a sentence ends with an \ldots, one is faced with the conundrum of how to properly terminate it. The "cleanest" way would of course be to add a terminating "period", thus signaling the reader that this grammatical unit has now reached completion. For instance,

$$ \rm{\ we\ have \ } \pi \approx 3.1415\ldots. \rm{\ However,} $$

We now have four dots at the end of the sentence, which seems like an excessive amount. The alternative however leaves a lingering feeling of dissatisfaction as the sentence does not feel finished:

$$ \rm{\ we\ have \ } \pi \approx 3.1415\ldots \rm{\ However,} $$

What is the best practice in such situations? Is there a "norm" to handle such a case when preparing a manuscript for publication?

Improve this question
$\endgroup$
12
  • 12
    $\begingroup$ To be pedantic, $\pi=3.1415\ldots$ whereas $\pi\approx 3.1415$. Boom, the problem goes away. $\endgroup$
    – Mark Grant
    Commented Jul 4, 2018 at 13:42
  • 11
    $\begingroup$ More seriously, I would suggest rewording the sentence so that it doesn't end with ellipses. $\endgroup$
    – Mark Grant
    Commented Jul 4, 2018 at 13:42
  • 5
    $\begingroup$ I think an English usage forum, like english.stackexchange.com, would be a better place to ask a question of this sort. $\endgroup$
    – Seva
    Commented Jul 4, 2018 at 13:43
  • 2
    $\begingroup$ I use period after \ldots, but I assume others do it differently. I hope this question was meant as a poll, as there is not really an answer. There is not even an agreement about periods at the end of sentences that end in displays! $\endgroup$
    – darij grinberg
    Commented Jul 4, 2018 at 13:48
  • 2
    $\begingroup$ @DimaPasechnik, occasionally, on tex.SE also minor things about typography are answered but generally question exclusively regarding typography is considered off-topic. Several proposals of typography.SE have to be done on area51 but none of them was successful. General questions about typography are currently answered on graphicdesign.SE. However, I think that this question could be answered on english.SE. $\endgroup$
    – gvgramazio
    Commented Jul 4, 2018 at 19:33

3 Answers 3

Reset to default
18
$\begingroup$

I believe papers in English should be written in full and correct English sentences, with any mathematical formula being part of a sentence. Therefore, I believe that the correct form in this case would be

we have $\pi=3.1415\ldots\;$. However,

-- not

we have $\pi=3.1415\ldots$ However,

(and not

we have $\pi \approx 3.1415\ldots\;$. However,

).

(I inserted an instance of \; after \ldots, trying to improve the spacing.)

Improve this answer
$\endgroup$
15
  • 4
    $\begingroup$ At least in spanish, the \ldots close the sentence, and there is no need of another period. $\endgroup$
    – efs
    Commented Jul 4, 2018 at 13:48
  • 7
    $\begingroup$ I agree with this answer. A related post about punctuation near math formulas is mathoverflow.net/questions/6675/…. $\endgroup$
    – KConrad
    Commented Jul 4, 2018 at 13:52
  • 1
    $\begingroup$ @KConrad : Thank you for your comment. I see that the most upvoted answer at the link you supplied offers a similar thought: "when one writes a mathematical text one is writing sentences, to which all rules which apply to sentences of course apply." $\endgroup$
    – Iosif Pinelis
    Commented Jul 4, 2018 at 14:16
  • 1
    $\begingroup$ Perhaps you should mention explicitly what you did, viz. to separate the three dots from the fourth dot by a thin space. $\endgroup$
    – Emil Jeřábek
    Commented Jul 4, 2018 at 14:22
  • 3
    $\begingroup$ Looking at this, it would appear that dots indicating some sort of abbreviation do replace the normal period at the end of a sentence in full and correct English sentences. Why is that different if a number is what's being abbreviated? (Honest question, as I'm not a native speaker.) $\endgroup$
    – Baum mit Augen
    Commented Jul 4, 2018 at 15:14
17
$\begingroup$

The principle mentioned by Iosif Pinelis that equations should follow the rules of grammar suggests to look at the OP in the broader context of the use of ellipsis in text: is $\ldots$ to be followed by a full stop period $.$ or not ?

The answer is "no" for British English (at least according to the University of Oxford Style Guide). For American English the answer is "yes" (at least for legal writing).

Improve this answer
$\endgroup$
6
  • $\begingroup$ A rule that equations should follow the rules of grammar does not imply a rule that the rules of grammar can override correct mathematical usage within/at the end of equations. In this case it's probably inconsequential to treat the ellipsis as both part of the equation and sentence termination, but in general there may be ambiguities introduced by this kind of practice, and I think the rule you cited should be interpreted as meaning "rephrase to avoid these cases". $\endgroup$
    – R.. GitHub STOP HELPING ICE
    Commented Jul 4, 2018 at 15:19
  • $\begingroup$ Interesting. In contrast, the same Wikipedia article says this about American English: " If an ellipsis ends the sentence, then there are three dots, each separated by a space [emphasis mine -- I.P.], followed by the final punctuation". However, I think that in our case these guidelines for British and American English do not necessarily apply, because \ldots is part of a math formula, and not an ellipsis between words in a sentence, $\endgroup$
    – Iosif Pinelis
    Commented Jul 4, 2018 at 15:22
  • 3
    $\begingroup$ @IosifPinelis But if we consider the math formula a part of a normal sentence, isn't the fact that the \ldots are set in math mode (as part of a math formula) a mere implementation detail? $\endgroup$
    – Baum mit Augen
    Commented Jul 4, 2018 at 15:25
  • $\begingroup$ @BaummitAugen : I think this not a question of implementation or typesetting mode. Rather, I think the single three-dot character produced by \ldots is just part of math formula. $\endgroup$
    – Iosif Pinelis
    Commented Jul 4, 2018 at 15:30
  • $\begingroup$ @IosifPinelis Thank you for your reply. However, I still do not see what exactly make the \ldots semantically different from "applicable to cats, dogs, …" (in which the '…' also appears as a single unicode character btw, in case that matters). $\endgroup$
    – Baum mit Augen
    Commented Jul 4, 2018 at 15:34
5
$\begingroup$

There are two possible correct answers.

  • The first one the the mathematician's: the ellipsis for some implied content thing that isn't written, while the full stop marks the end of a sentence. Since each of the two typographical signs has its own functions, both should be present. This is logically correct, but typographically wrong. :)

  • The second one is the typographer's, and it is better illustrated by the following three situations:

    1. Whenever a sentence contains an ellipsis right before the full stop, the full stop is no longer written.
    2. Whenever a sentence ends with an abbreviation (containing dots, such as "U.S.A." or "etc."), the full stop is no longer written (see also the links therein).
    3. Whenever a sentence ends with a quotation that itself ends with a full stop, the "outer" full stop is no longer written (it is a matter of debate, though, whether the remaining full stop should be inside or outside the quotation marks). Follow the links in the answers given here and see also this answer citing the Chicago Manual of Style.

To conclude, whenever a full stop would logically follow another typographical sign that itself ends with a dot, the full stop is no longer written (it "fuses" with the one preceding it).

Improve this answer
$\endgroup$
5
  • 1
    $\begingroup$ Consider an excerpt from an imaginary text for math-phobic students, where removal of the period results in uncomfortable ambiguity. Choice 1: "The arclength $L$ subtended by the angle POQ is given by the formula $L=\pi RA/180$. Recall that $\pi$ is Ludolph’s constant, $3.14159\ldots$ . $R$ is the radial length, and $A$ is the measure of the angle POQ in degrees." Choice 2: "The arclength $L$ subtended by the angle POQ is given by the formula $L=\pi RA/180$. Recall that $\pi$ is Ludolph’s constant, $3.14159\ldots R$ is the radial length, and $A$ is the measure of the angle POQ in degrees." $\endgroup$
    – Todd Trimble
    Commented Jul 4, 2018 at 21:13
  • $\begingroup$ The link you gave for item 1 confirms that Oxford prescribes the "no fourth dot" style. But scrolling up a little on the page, I see that this is not the unanimous decision of all styles. $\endgroup$
    – Andreas Blass
    Commented Jul 4, 2018 at 22:11
  • $\begingroup$ I believe that the current "consensus" (if such exists - it's at least a trend) on periods at the end of quotations is predicated on whether or not the period belongs with the quoted sentence - (He said, "No, thank you.") vs (He spoke about "stuff".) $\endgroup$
    – Sam Benner
    Commented Jul 4, 2018 at 22:22
  • $\begingroup$ @ToddTrimble: You are cheating :) because you ignore spacing. You use $3.14159 \ldots R$ instead of, at least, $3.14159 \ldots$ $R$, which would allow TeX to insert better spacing. Even better, you could manually force clearer spacing with appropriate LaTeX commands. Note that all the style and typographical conventions texts found in the links I provided insist on the importance of spacing even more than on the importance of punctuation. $\endgroup$
    – Alex M.
    Commented Jul 5, 2018 at 9:13
  • $\begingroup$ I don't believe that any sentence about TeX starting with "Even better, you could manually force clearer spacing" is good advice. (If you know how to insert correct spacing, you will do so and don't need the advice. If you don't know how to insert correct spacing, then TeX will do a better job than you do, even if it's not perfect.) $\endgroup$
    – LSpice
    Commented Feb 20, 2019 at 15:55

Not the answer you're looking for? Browse other questions tagged .