overabundance vs excess

overabundance and excess both are nouns.

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

As nouns, excess is a hyponym of overabundance; that is, excess is a word with a more specific, narrower meaning than overabundance:

Other hyponyms of overabundance include nimiety, surplus, surplusage, glut, oversupply, surfeit, bellyful.

As nouns, overabundance and excess are synonyms defined as:

Other synonyms of overabundance include surfeit.

overabundance (noun)	excess (noun)
a quantity that is more than what is appropriate	excessive indulgence
the state of being more than full	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

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