ratio. The ratio of two quantities expressed in terms of the same unit is the fraction that has the first quantity as numerator and the second as denominator. For example, if in a group of 100 people 5 die, the ratio of deaths to the total number in the group is 5/100 = 1/20 = .05. Ratios are indicated also by writing the two values with a colon between them, e.g., the ratio of 4 to 8 can be expressed by 4:8 as well as by 4/8.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.