copious vs plenteous

copious and plenteous both are adjectives.

Word	Noun	Adjective	Verb	Adverb
copious	No	Yes	No	No
plenteous	No	Yes	No	No

As adjectives, copious and plenteous are synonyms defined as:

Other synonyms of copious include ample, plentiful, rich.

copious (adjective)	plenteous (adjective)
affording an abundant supply	affording an abundant supply
large in number or quantity (especially of discourse)