planaria vs planarian

planaria and planarian both are nouns.

Word	Noun	Adjective	Verb	Adverb
planaria	Yes	No	No	No
planarian	Yes	No	No	No

As nouns, planaria and planarian are synonyms defined as:

planaria and planarian: free-swimming mostly freshwater flatworms; popular in laboratory studies for the ability to regenerate lost parts

planaria (noun)	planarian (noun)
free-swimming mostly freshwater flatworms; popular in laboratory studies for the ability to regenerate lost parts	free-swimming mostly freshwater flatworms; popular in laboratory studies for the ability to regenerate lost parts