We may also say a copious rain; but copious can be applied to thought, language, etc., where plentiful can not well be used. Neither affluent, copious, nor plentiful can be used of time or space; a field is sometimes called plentiful, not with reference to its extent, but to its productiveness.

J. C. Fernald, English Synonyms and Antonyms (1914)

Example sentences

abundant Fossil fuels are abundant in that vast continent.
ample Ten million yen will be ample for the project.
plentiful For some, excuses are plentiful to remain idle.
profuse He was profuse in his praise of his teacher.
voluminous A voluminous robe hid the contours of the body underneath.

Popularity over time

Word	1850 → 2019	Trend
copious		steady
abundant		falling
ample		falling
plentiful		falling
profuse		steady

Use in printed books, per decade from 1850 to 2019.

By length

4 letters: full¹, rich¹
5 letters: flush¹, ample²
6 letters: lavish², galore², effuse
7 letters: liberal³, diffuse², teeming², profuse²
8 letters: abundant³, fruitful², prodigal³, lackless
9 letters: redundant³, plentiful³, exuberant⁴, bountiful³, abounding³, luxuriant⁴, bounteous, plenteous
10 letters: voluminous⁴

The small number after each word is its number of syllables (ample² = 2 syllables).

In other languages

Français: copieux
Italiano: copioso
Español: copioso
Català: copiós