Pain & Pleasure

Far back in evolutionary history, if an organism felt nothing while it was being injured, then that organism would not have felt compelled to avoid the injury. If, on the other hand, the organism felt something strongly disagreeable when it was being damaged, then it would have been much more likely to move away from the source of harm, thereby surviving longer to reproduce. For this reason, pain was born into the world.

Pain is a negative feeling from some stimulus, physical or mental.

Agony and misery are extremes of pain.