Rolaids vs gastric antacid

Rolaids and gastric antacid both are nouns.

Word	Noun	Adjective	Verb	Adverb
Rolaids	Yes	No	No	No
gastric antacid	Yes	No	No	No

As nouns, gastric antacid is a hypernym of Rolaids; that is, gastric antacid is a word with a broader meaning than Rolaids:

Rolaids: an antacid
gastric antacid: an agent that counteracts or neutralizes acidity (especially in the stomach)

Other hypernyms of Rolaids include alkaliser, alkalizer, antacid, antiacid.

Rolaids (noun)	gastric antacid (noun)
an antacid	an agent that counteracts or neutralizes acidity (especially in the stomach)