common duckweed vs lesser duckweed

common duckweed and lesser duckweed both are nouns.

Word	Noun	Adjective	Verb	Adverb
common duckweed	Yes	No	No	No
lesser duckweed	Yes	No	No	No

As nouns, common duckweed and lesser duckweed are synonyms defined as:

common duckweed and lesser duckweed: of temperate regions except eastern Asia and Australia

Other synonyms of common duckweed include Lemna minor.

common duckweed (noun)	lesser duckweed (noun)
of temperate regions except eastern Asia and Australia	of temperate regions except eastern Asia and Australia