natural philosophy vs critical

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

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

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

natural philosophy (adjective)	critical (adjective)
	marked by a tendency to find and call attention to errors and flaws
	characterized by careful evaluation and judgment
	being in or verging on a state of crisis or emergency
	at or of a point at which a property or phenomenon suffers an abrupt change especially having enough mass to sustain a chain reaction
	of or involving or characteristic of critics or criticism
	forming or having the nature of a turning point or crisis
	urgently needed; absolutely necessary