natural philosophy vs rest mass

natural philosophy and rest mass both are nouns.

Word	Noun	Adjective	Verb	Adverb
natural philosophy	Yes	No	No	No
rest mass	Yes	No	No	No

natural philosophy (noun)	rest mass (noun)
the science of matter and energy and their interactions	(physics) the mass of a body as measured when the body is at rest relative to an observer, an inherent property of the body