lozenge vs cough drop

lozenge and cough drop both are nouns.

Word	Noun	Adjective	Verb	Adverb
lozenge	Yes	No	No	No
cough drop	Yes	No	No	No

As nouns, cough drop is a hyponym of lozenge; that is, cough drop is a word with a more specific, narrower meaning than lozenge:

Other hyponyms of lozenge include cachou, pastil, pastille, troche.

lozenge (noun)	cough drop (noun)
a dose of medicine in the form of a small pellet	a medicated lozenge used to soothe the throat
a small aromatic or medicated candy