phosphorus vs phosphorous

phosphorus is a noun but phosphorous is not a noun.

Word	Noun	Adjective	Verb	Adverb
phosphorus	Yes	No	No	No
phosphorous	No	Yes	No	No

phosphorus (noun)	phosphorous (noun)
a multivalent nonmetallic element of the nitrogen family that occurs commonly in inorganic phosphate rocks and as organic phosphates in all living cells; is highly reactive and occurs in several allotropic forms

phosphorus (adjective)	phosphorous (adjective)
	containing or characteristic of phosphorus