yawn vs reflex response

yawn and reflex response both are nouns.

Word	Noun	Adjective	Verb	Adverb
yawn	Yes	No	Yes	No
reflex response	Yes	No	No	No

As nouns, reflex response is a hypernym of yawn; that is, reflex response is a word with a broader meaning than yawn:

yawn: an involuntary intake of breath through a wide open mouth; usually triggered by fatigue or boredom
reflex response: an automatic instinctive unlearned reaction to a stimulus

yawn (noun)	reflex response (noun)
an involuntary intake of breath through a wide open mouth; usually triggered by fatigue or boredom	an automatic instinctive unlearned reaction to a stimulus

yawn (verb)	reflex response (verb)
utter a yawn, as from lack of oxygen or when one is tired
be wide open