The word 'hypnotic' is a noun and an adjective.
The noun 'hypnotic' is a word for a sleep-inducing drug.
The adjective 'hypnotic' describes a noun as tending to cause sleep; of or relating to hypnosis or hypnotism.
Example sentences:
This medication is a hypnotic, it will make you sleepy. (noun)
I was rocked to sleep by the hypnotic motion of the train. (adjective)