tunic vs kirtle

tunic and kirtle both are nouns.

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

As nouns, kirtle is a hyponym of tunic; that is, kirtle 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
kirtle: a garment resembling a tunic that was worn by men in the Middle Ages

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

tunic (noun)	kirtle (noun)
any of a variety of loose fitting cloaks extending to the hips or knees	a long dress worn by women
an enveloping or covering membrane or layer of body tissue	a garment resembling a tunic that was worn by men in the Middle Ages