hard drug vs cocaine

hard drug and cocaine both are nouns.

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

As nouns, cocaine is a hyponym of hard drug; that is, cocaine is a word with a more specific, narrower meaning than hard drug:

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

Other hyponyms of hard drug include cocain, diacetylmorphine, heroin.

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