I think it's fair to say "quicksort is not stable" if you want. You need some definition of what the parameters of the algorithm is, when you describe it. What

I think it's fair to say "quicksort is not stable" if you want. You need some definition of what the parameters of the algorithm is, when you describe it. What should be mentioned is that there's a variant (requiring memory XYZ) that is stable. It would be fair to call it a variant of the quicksort algorithm.