change posture vs sit

change posture and sit both are verbs.

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

As verbs, sit is a hyponym of change posture; that is, sit is a word with a more specific, narrower meaning than change posture:

change posture (verb)	sit (verb)
undergo a change in bodily posture	serve in a specific professional capacity
	be in a position in which one's upper body is largely upright and supported by one's backside
	show to a seat; assign a seat for
	take a seat
	be in session
	sit and travel on the back of animal, usually while controlling its motions
	assume a posture as for artistic purposes
	work or act as a baby-sitter
	be around, often idly or without specific purpose
	be located or situated somewhere