planation vs erosion

planation and erosion both are nouns.

Word	Noun	Adjective	Verb	Adverb
planation	Yes	No	No	No
erosion	Yes	No	No	No

As nouns, erosion is a hypernym of planation; that is, erosion is a word with a broader meaning than planation:

planation: the process of erosion whereby a level surface is produced
erosion: (geology) the mechanical process of wearing or grinding something down (as by particles washing over it), also figuratively

Other hypernyms of planation include eating away, eroding, wearing, wearing away.

planation (noun)	erosion (noun)
the process of erosion whereby a level surface is produced	(geology) the mechanical process of wearing or grinding something down (as by particles washing over it), also figuratively
	erosion by chemical action
	a gradual decline of something
	condition in which the earth's surface is worn away by the action of water and wind