potassium bromide vs restrainer

potassium bromide and restrainer both are nouns.

Word	Noun	Adjective	Verb	Adverb
potassium bromide	Yes	No	No	No
restrainer	Yes	No	No	No

As nouns, restrainer is a hypernym of potassium bromide; that is, restrainer is a word with a broader meaning than potassium bromide:

potassium bromide: a white crystalline salt (KBr) used as a sedative and in photography
restrainer: a chemical that is added to a photographic developer in order to retard development and reduce the amount of fog on a film

Other hypernyms of potassium bromide include salt.

potassium bromide (noun)	restrainer (noun)
a white crystalline salt (KBr) used as a sedative and in photography	a person who directs and restrains
	a chemical that is added to a photographic developer in order to retard development and reduce the amount of fog on a film