copious vs plentiful

copious and plentiful both are adjectives.

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

As adjectives, copious and plentiful are synonyms defined as:

Other synonyms of copious include ample, plenteous, rich.

copious (adjective)	plentiful (adjective)
affording an abundant supply	producing in abundance
large in number or quantity (especially of discourse)	affording an abundant supply
	existing in great number or quantity