hollow-back vs lordosis

hollow-back and lordosis both are nouns.

Word	Noun	Adjective	Verb	Adverb
hollow-back	Yes	No	No	No
lordosis	Yes	No	No	No

As nouns, hollow-back and lordosis are synonyms defined as:

hollow-back and lordosis: an abnormal inward (forward) curvature of the vertebral column

hollow-back (noun)	lordosis (noun)
an abnormal inward (forward) curvature of the vertebral column	an abnormal inward (forward) curvature of the vertebral column