compression ratio vs ratio

compression ratio and ratio both are nouns.

Word	Noun	Adjective	Verb	Adverb
compression ratio	Yes	No	No	No
ratio	Yes	No	No	No

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

compression ratio: for a gas compressor, the discharge pressure divided by the suction pressure.
ratio: the relative magnitudes of two quantities (usually expressed as a quotient)

compression ratio (noun)	ratio (noun)
for a gas compressor, the discharge pressure divided by the suction pressure.	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)