lordosis vs hollow-back

lordosis and hollow-back both are nouns.

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

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

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

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