In a mathematical model, I have a set $J$ of distinct jobs, and a constraint dealing with pairs of elements from the job set. Which of the following is the most accurate way to address two jobs $j$ and $j'$ from the set $J$?

  1. $j,j' \in J$

  2. $(j,j') \in J$

  3. $j,j' \in J^2$

  4. $(j,j') \in J^2$

In short, I want to know whether I need brackets, and the set should be $J$, or $J^2$?

** Perhaps a basic question, but I want to be accurate in my writing.

  • $\begingroup$ From the perspective of a guy who have little experience in math, 1. is the easiest to understand (and 5. of Rob Pratt answer if you want to be more correct). $\endgroup$
    – mrBen
    Mar 4, 2020 at 12:22

1 Answer 1


Definitely not 2 or 3. 1 is often used but a little informal. 4 is most accurate. Two more suggestions:

  1. $j\in J,\ j'\in J$
  2. $(j,j')\in J\times J$

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