peneplain vs peneplane

peneplain and peneplane both are nouns.

Word	Noun	Adjective	Verb	Adverb
peneplain	Yes	No	No	No
peneplane	Yes	No	No	No

As nouns, peneplain and peneplane are synonyms defined as:

peneplain and peneplane: a more or less level land surface representing an advanced stage of erosion undisturbed by crustal movements

peneplain (noun)	peneplane (noun)
a more or less level land surface representing an advanced stage of erosion undisturbed by crustal movements	a more or less level land surface representing an advanced stage of erosion undisturbed by crustal movements