# Mathematical notation for redefined set?

I have a set of numbers (W), from which I am only keeping those greater than 5.

I want to state that the set W has been redefined to only include the subset of values greater than 5, but want to avoid giving the new set a new name, because I already have too many variables, and I want readers to associate W with the new set. Is there a way of referring to the redefined set W? I've been using W ' in my notes, but this could be misleading to others ...

W={1,3,5,2,7,9,10,18}

W '={7,9,10,18}

Apologies if this is a naive question - it has been a while since I had to write my code in proper notation!

• This is generally accepted. Use $:=$ for definitions and you have to care about ambiguity. You could even define your own notation, for example $W_{>5}$, however $W'$ is totally fine. Aug 5, 2013 at 13:24
• Thanks! so just to clarify, I should write W := {1,3,5,2,7,9,10,18} W ':= {7,9,10,18} ? Aug 5, 2013 at 13:26
• Yes. Write $W:=\{1,3,5,2,7,9,10,18\}$ and $W':=\{7,9,10,18\}$ and everyone will know what your intention is. Aug 5, 2013 at 13:27
• Super - thanks again! Aug 5, 2013 at 13:29

When someone sees $\Bbb Z^{\geq 0}$ or $\Bbb Z_{\geq0}$, they would instantly know the meaning of the notation (well, in the generic case). If there is a natural ordering on your set, e.g. a set of integers or real numbers, the writing $W^{\geq 5}$ or $W^{>5}$ (or with a subscript) is fine.