Noun the quantitative relation between two amounts showing the number of times one value contains or is contained within the other. "the ratio of men's jobs to women's is 8 to 1" synonyms: proportion, comparative number, correlation, relationship, correspondence; More the relative value of silver and gold in a bimetallic system of currency.
symbol means intersection, so everything that is in both sets, and the 
symbol means union, so the two sets combined.
