psychoactive substance vs drug

psychoactive substance and drug both are nouns.

Word	Noun	Adjective	Verb	Adverb
psychoactive substance	Yes	No	No	No
drug	Yes	No	Yes	No

As nouns, drug is a hypernym of psychoactive substance; that is, drug is a word with a broader meaning than psychoactive substance:

psychoactive substance: a drug that can produce mood changes and distorted perceptions
drug: a substance that is used as a medicine or narcotic

psychoactive substance (noun)	drug (noun)
a drug that can produce mood changes and distorted perceptions	a substance that is used as a medicine or narcotic

psychoactive substance (verb)	drug (verb)
	administer a drug to
	use recreational drugs