surplus vs supernumerary

surplus and supernumerary both are nouns.

Word	Noun	Adjective	Verb	Adverb
surplus	Yes	Yes	No	No
supernumerary	Yes	Yes	No	No

As adjectives, surplus and supernumerary are synonyms defined as:

Other synonyms of surplus include excess, extra, redundant, spare, supererogatory, superfluous.

surplus (noun)	supernumerary (noun)
a quantity much larger than is needed	a minor actor in crowd scenes
	a person serving no apparent function

surplus (adjective)	supernumerary (adjective)
more than is needed, desired, or required	more than is needed, desired, or required