hunch vs change posture

hunch is a noun but change posture is not a noun.

Word	Noun	Adjective	Verb	Adverb
hunch	Yes	No	Yes	No
change posture	No	No	Yes	No

As verbs, change posture is a hypernym of hunch; that is, change posture is a word with a broader meaning than hunch:

hunch: round one's back by bending forward and drawing the shoulders forward
change posture: undergo a change in bodily posture

hunch (noun)	change posture (noun)
the act of bending yourself into a humped position
an impression that something might be the case

hunch (verb)	change posture (verb)
round one's back by bending forward and drawing the shoulders forward	undergo a change in bodily posture