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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.

4. the final argument of kings (a resort to arms): motto engraved on the cannon of Louis XIV.

5. a measure of the relative size of two classes expressible as a proportion: the ratio of boys to girls is 2 to 1

6. (maths) a quotient of two numbers or quantities See also proportion (sense 6)