If you say that x is not saltier than y, you are saying that they are equally salty.X is not as salty as Y.
X is less salty than Y.
Can we also say X is not saltier than Y. I mean is this structure correct ,or we should necessarily use less?
If you say that x is not saltier than y, you are saying that they are equally salty.
Perhaps, but why not simply say: "I am shorter than/not as tall as you".If I say I am not taller than you, I may be as tall if not shorter than you. No?
Let's take the OP's original example of saltiness. If I taste x and y and I find that x is less salty, I will say that it is less salty. If I taste and say that it is not saltier (I wouldn't say that), it means that it is equally salty.Well, this is something you can't be sure of until you do the measurement to be exact.
That's correct.Equally or less salty.