aorta vs aortic arch

aorta and aortic arch both are nouns.

Word	Noun	Adjective	Verb	Adverb
aorta	Yes	No	No	No
aortic arch	Yes	No	No	No

As nouns, aortic arch is a hyponym of aorta; that is, aortic arch is a word with a more specific, narrower meaning than aorta:

aorta: the large trunk artery that carries blood from the left ventricle of the heart to branch arteries
aortic arch: the part of the aorta that arches and turns downward

Other hyponyms of aorta include ascending aorta, descending aorta, abdominal aorta, thoracic aorta.

aorta (noun)	aortic arch (noun)
the large trunk artery that carries blood from the left ventricle of the heart to branch arteries	the part of the aorta that arches and turns downward