P/E ratio vs ratio

P/E ratio and ratio both are nouns.

Word	Noun	Adjective	Verb	Adverb
P/E ratio	Yes	No	No	No
ratio	Yes	No	No	No

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

P/E ratio: (stock market) the price of a stock divided by its earnings
ratio: the relative magnitudes of two quantities (usually expressed as a quotient)

P/E ratio (noun)	ratio (noun)
(stock market) the price of a stock divided by its earnings	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)