surplus vs excess

surplus and excess both are nouns.

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

As adjectives, surplus and excess are synonyms defined as:

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

As nouns, surplus and excess are synonyms defined as:

Other synonyms of surplus include nimiety, surplusage.

surplus (noun)	excess (noun)
a quantity much larger than is needed	excessive indulgence
	immoderation as a consequence of going beyond sufficient or permitted limits
	a quantity much larger than is needed
	the state of being more than full

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