Difference between Abyss and Abysm

Abyss

Part of speech: noun

Definition: A bottomless or unfathomed depth, gulf, or chasm; hence, any deep, immeasurable, and, specifically, hell, or the bottomless pit. Infinite time; a vast intellectual or moral depth. The center of an escutcheon.

Example sentence: If you understand hallucination and illusion, you don't blindly follow any leader. You must know if the person is sane or insane, over the abyss.

Abysm

Part of speech: noun

Definition: An abyss; a gulf, a chasm, a very deep hole