betting odds vs ratio

betting odds and ratio both are nouns.

Word	Noun	Adjective	Verb	Adverb
betting odds	Yes	No	No	No
ratio	Yes	No	No	No

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

betting odds: the ratio by which one better's wager is greater than that of another
ratio: the relative magnitudes of two quantities (usually expressed as a quotient)

betting odds (noun)	ratio (noun)
the ratio by which one better's wager is greater than that of another	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)