excess vs overabundance

excess and overabundance both are nouns.

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

As nouns, overabundance is a hypernym of excess; that is, overabundance is a word with a broader meaning than excess:

Other hypernyms of excess include overmuch, overmuchness, superabundance.

As nouns, excess and overabundance are synonyms defined as:

Other synonyms of excess include surfeit.

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

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