If you divide the number of elements in a sample with a specific characteristic by the total number of elements in the sample, the dividend is the:

In general, this would be a ratio. However, if the ratio is the number of items with specific characteristic to the total number of elements, then this would be a probability. The dividend is the numerator, and the divisor is the denominator. For example, if there are 5 white balls out of 6 balls, the probability of getting a white ball would be 5/6. The dividend here is 5.