water lettuce vs water cabbage

water lettuce and water cabbage both are nouns.

Word	Noun	Adjective	Verb	Adverb
water lettuce	Yes	No	No	No
water cabbage	Yes	No	No	No

As nouns, water lettuce and water cabbage are synonyms defined as:

water lettuce and water cabbage: pantropical floating plant forming a rosette of wedge-shaped leaves; a widespread weed in rivers and lakes

Other synonyms of water lettuce include pistia, Pistia stratiotes, Pistia stratoites.

water lettuce (noun)	water cabbage (noun)
pantropical floating plant forming a rosette of wedge-shaped leaves; a widespread weed in rivers and lakes	pantropical floating plant forming a rosette of wedge-shaped leaves; a widespread weed in rivers and lakes