cocaine vs hard drug

cocaine and hard drug both are nouns.

Word	Noun	Adjective	Verb	Adverb
cocaine	Yes	No	No	No
hard drug	Yes	No	No	No

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

cocaine: a narcotic (alkaloid) extracted from coca leaves; used as a surface anesthetic or taken for pleasure; can become powerfully addictive
hard drug: a narcotic that is considered relatively strong and likely to cause addiction

cocaine (noun)	hard drug (noun)
a narcotic (alkaloid) extracted from coca leaves; used as a surface anesthetic or taken for pleasure; can become powerfully addictive	a narcotic that is considered relatively strong and likely to cause addiction