factor of safety vs ratio

factor of safety and ratio both are nouns.

Word	Noun	Adjective	Verb	Adverb
factor of safety	Yes	No	No	No
ratio	Yes	No	No	No

As nouns, ratio is a hypernym of factor of safety; that is, ratio is a word with a broader meaning than factor of safety:

factor of safety: the ratio of the breaking stress of a structure to the estimated maximum stress in ordinary use
ratio: the relative magnitudes of two quantities (usually expressed as a quotient)

factor of safety (noun)	ratio (noun)
the ratio of the breaking stress of a structure to the estimated maximum stress in ordinary use	the relation between things (or parts of things) with respect to their comparative quantity, magnitude, or degree
	the relative magnitudes of two quantities (usually expressed as a quotient)