cephalic index vs ratio

cephalic index and ratio both are nouns.

Word	Noun	Adjective	Verb	Adverb
cephalic index	Yes	No	No	No
ratio	Yes	No	No	No

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

cephalic index: ratio (in percent) of the maximum breadth to the maximum length of a skull
ratio: the relative magnitudes of two quantities (usually expressed as a quotient)

cephalic index (noun)	ratio (noun)
ratio (in percent) of the maximum breadth to the maximum length of a skull	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)