That is ample which gives a safe, but not a large, margin beyond a given demand; that is abundant, affluent, bountiful, liberal, plentiful, which is largely in excess of manifest need.

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.
copious Giraffes consume copious amounts of acacia leaves.
bountiful Farmers harvested a bountiful oat crop this season.
bottomless Ziri was afraid to fall into a bottomless pit.

Popularity over time

Word	1850 → 2019	Trend
plentiful		falling
abundant		falling
ample		falling
copious		steady
bountiful		rising

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

By length

4 letters: rich¹, rife¹
5 letters: ample²
6 letters: lavish², galore²
7 letters: fertile², copious³, teeming², replete², profuse²
8 letters: numerous³, generous³, adequate³, abundant³, prolific³, fruitful²
9 letters: bountiful³, abounding³, luxuriant⁴, bounteous, plenteous
10 letters: sufficient³, bottomless³

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