# Math spacing when using quantifiers [closed]

I'm often writing equations with quantifiers like these:

\begin{equation*}
x_i \quad \forall i = 1, \dotsc, n
\end{equation*}


I've read this answer, but I'm not sure if my case is an example for a situation where one uses EM quad.

So my first question is, would you put a \quad space at that position?

The second question is, would you separate the first part from the quantifier with a comma like:

\begin{equation*}
x_i \quad , \forall i = 1, \dotsc, n
\end{equation*}


## closed as primarily opinion-based by egreg, Stefan Pinnow, Mensch, Paul Gaborit, JesseDec 7 '16 at 13:37

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

• Personally, I'd avoid the \forall: x_{i},\qquad i=1,2,\dots,n I think that the quantifier is even mathematically wrong (at least in several cases I see). Note that you don't need \dotsc, because \dots is able to figure out what follows. \dotsc is needed only if you have an open ended enumeration, such as i=1,2,\dotsc – egreg Nov 20 '15 at 21:41
• (1) I'd never leave a floating comma. (2) in most of what I edit I use a qquad for this leaving the single quad for "f quad and quad g qquad for all..." – daleif Nov 20 '15 at 21:42
• Logically, \forall seems wrong. I don't know if mathematicians use it differently. Or don't remember well enough to be sure. But logically, it doesn't make sense. – cfr Nov 20 '15 at 22:52
• @cfr assuming x_i is a boolean valued predicate, then it makes sense although would more normally be written with the quantifier first, \forall i \in \{1,\dots\n\} . x_i – David Carlisle Nov 20 '15 at 23:27
• @DavidCarlisle It was more the = combined with the \forall which didn't make sense. (Although, logically, I'm inclined to see the i in x_i as unbound.) \forall i \in \{... for \text{for } i=1,\dots. It's the combination which doesn't look wff-like to me. – cfr Nov 20 '15 at 23:45

Don't put a space before the comma, Also I would not use \forall with an informal iterator displayed as dots.

Assuming x_i is some boolean valued expression indexed by i then either

\begin{equation*}
x_i \quad \text{for all $i=1,\dots,n$}
\end{equation*}


or more formally

\begin{equation*}
\forall i \in \{1,\dots,n\}\mathbin{.}x_i
\end{equation*}