Robitussin vs expectorant

Robitussin and expectorant both are nouns.

Word	Noun	Adjective	Verb	Adverb
Robitussin	Yes	No	No	No
expectorant	Yes	No	No	No

As nouns, expectorant is a hypernym of Robitussin; that is, expectorant is a word with a broader meaning than Robitussin:

Robitussin: trade name of an expectorant that loosens phlegm and makes it easier to cough up
expectorant: a medicine promoting expectoration

Other hypernyms of Robitussin include expectorator.

Robitussin (noun)	expectorant (noun)
trade name of an expectorant that loosens phlegm and makes it easier to cough up	a medicine promoting expectoration