breathe vs yawn

breathe is not a noun while yawn is a noun.

Word	Noun	Adjective	Verb	Adverb
breathe	No	No	Yes	No
yawn	Yes	No	Yes	No

As verbs, yawn is a hyponym of breathe; that is, yawn is a word with a more specific, narrower meaning than breathe:

breathe (noun)	yawn (noun)
	an involuntary intake of breath through a wide open mouth; usually triggered by fatigue or boredom

breathe (verb)	yawn (verb)
draw air into, and expel out of, the lungs	utter a yawn, as from lack of oxygen or when one is tired
expel (gases or odors)	be wide open
reach full flavor by absorbing air and being let to stand after having been uncorked
take a short break from one's activities in order to relax
utter or tell
manifest or evince
impart as if by breathing
be alive
allow the passage of air through