arcus senilis vs arcus

arcus senilis and arcus both are nouns.

Word	Noun	Adjective	Verb	Adverb
arcus senilis	Yes	No	No	No
arcus	Yes	No	No	No

As nouns, arcus senilis and arcus are synonyms defined as:

arcus senilis and arcus: a whitish deposit in the shape of an arc that is sometimes seen in the cornea

arcus senilis (noun)	arcus (noun)
a whitish deposit in the shape of an arc that is sometimes seen in the cornea	a whitish deposit in the shape of an arc that is sometimes seen in the cornea