lumber vs planking

lumber and planking both are nouns.

Word	Noun	Adjective	Verb	Adverb
lumber	Yes	No	Yes	No
planking	Yes	No	No	No

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

Other hyponyms of lumber include stock, strip, board, plank.

lumber (noun)	planking (noun)
an implement used in baseball by the batter	the work of covering an area with planks
the wood of trees cut and prepared for use as building material	(nautical) a covering or flooring constructed of planks (as on a ship)
	planks collectively; a quantity of planks

lumber (verb)	planking (verb)
cut lumber, as in woods and forests
move heavily or clumsily