voluminous vs copious

voluminous and copious both are adjectives.

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

As adjectives, voluminous and copious are synonyms defined as:

voluminous and copious: large in number or quantity (especially of discourse)

voluminous (adjective)	copious (adjective)
large in number or quantity (especially of discourse)	affording an abundant supply
marked by repeated turns and bends	large in number or quantity (especially of discourse)
large in volume or bulk