tunic vs chiton

tunic and chiton both are nouns.

Word	Noun	Adjective	Verb	Adverb
tunic	Yes	No	No	No
chiton	Yes	No	No	No

As nouns, chiton is a hyponym of tunic; that is, chiton is a word with a more specific, narrower meaning than tunic:

tunic: any of a variety of loose fitting cloaks extending to the hips or knees
chiton: a woolen tunic worn by men and women in ancient Greece

Other hyponyms of tunic include gymslip, kameez, kirtle, surcoat, tabard.

tunic (noun)	chiton (noun)
any of a variety of loose fitting cloaks extending to the hips or knees	primitive elongated bilaterally symmetrical marine mollusk having a mantle covered with eight calcareous plates
an enveloping or covering membrane or layer of body tissue	a woolen tunic worn by men and women in ancient Greece