xiphoid process vs os

xiphoid process and os both are nouns.

Word	Noun	Adjective	Verb	Adverb
xiphoid process	Yes	No	No	No
os	Yes	No	No	No

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

xiphoid process: smallest of the three parts of the breastbone; articulates with the corpus sternum and the seventh rib
os: rigid connective tissue that makes up the skeleton of vertebrates

Other hypernyms of xiphoid process include bone.

xiphoid process (noun)	os (noun)
smallest of the three parts of the breastbone; articulates with the corpus sternum and the seventh rib	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening