natural philosophy vs metastable

natural philosophy is a noun but metastable is not a noun.

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

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

natural philosophy (adjective)	metastable (adjective)
	(of physical systems) continuing in its present state of equilibrium unless sufficiently disturbed to pass to a more stable state of equilibrium