Pronunciation: (rā'shō, -shē-ō"),[key] —n., —pl.-tios. 1. the relation between two similar magnitudes with respect to the number of times the first contains the second: the ratio of 5 to 2, written 5:2 or 5/2. 2. proportional relation; rate: the ratio between acceptances and rejections. 3. Finance.the relative value of gold and silver in a bimetallic currency system.