fissile vs natural philosophy

fissile is not a noun while natural philosophy is a noun.

Word	Noun	Adjective	Verb	Adverb
fissile	No	Yes	No	No
natural philosophy	Yes	No	No	No

fissile (noun)	natural philosophy (noun)
	the science of matter and energy and their interactions

fissile (adjective)	natural philosophy (adjective)
capable of being split or cleft or divided in the direction of the grain
capable of undergoing nuclear fission