champaign vs peneplain

champaign and peneplain both are nouns.

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

As nouns, peneplain is a hyponym of champaign; that is, peneplain is a word with a more specific, narrower meaning than champaign:

champaign: extensive tract of level open land
peneplain: a more or less level land surface representing an advanced stage of erosion undisturbed by crustal movements

Other hyponyms of champaign include flat, flood plain, floodplain, llano, moor, moorland, peneplane, snowfield, steppe, tundra.

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