hipbone vs os

hipbone and os both are nouns.

Word	Noun	Adjective	Verb	Adverb
hipbone	Yes	No	No	No
os	Yes	No	No	No

As nouns, os is a hypernym of hipbone; that is, os is a word with a broader meaning than hipbone:

hipbone: large flaring bone forming one half of the pelvis; made up of the ilium and ischium and pubis
os: rigid connective tissue that makes up the skeleton of vertebrates

Other hypernyms of hipbone include bone.

hipbone (noun)	os (noun)
large flaring bone forming one half of the pelvis; made up of the ilium and ischium and pubis	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening