yak vs ox

yak and ox both are nouns.

Word	Noun	Adjective	Verb	Adverb
yak	Yes	No	Yes	No
ox	Yes	No	No	No

As nouns, ox is a hypernym of yak; that is, ox is a word with a broader meaning than yak:

yak: large long-haired wild ox of Tibet often domesticated
ox: any of various wild bovines especially of the genera Bos or closely related Bibos

Other hypernyms of yak include wild ox.

yak (noun)	ox (noun)
large long-haired wild ox of Tibet often domesticated	any of various wild bovines especially of the genera Bos or closely related Bibos
noisy talk	an adult castrated bull of the genus Bos; especially Bos taurus

yak (verb)	ox (verb)
talk profusely