belch vs physiological reaction

belch and physiological reaction both are nouns.

Word	Noun	Adjective	Verb	Adverb
belch	Yes	No	Yes	No
physiological reaction	Yes	No	No	No

As nouns, physiological reaction is a hypernym of belch; that is, physiological reaction is a word with a broader meaning than belch:

belch: a reflex that expels gas noisily from the stomach through the mouth
physiological reaction: an automatic instinctive unlearned reaction to a stimulus

belch (noun)	physiological reaction (noun)
a reflex that expels gas noisily from the stomach through the mouth	an automatic instinctive unlearned reaction to a stimulus

belch (verb)	physiological reaction (verb)
expel gas from the stomach
become active and spew forth lava and rocks