From AMS Glossary
One of several measures of central tendency.
1) Pertaining to a series of numbers, the median is the middle term when the numbers are arranged in algebraic order. If the number of terms is even, the median is taken as halfway between the two middle terms. 2) Pertaining to a continuous random variable x, the median is that value that divides the probability distribution into two equal areas. Hence, in terms of the distribution function F(x), the median is that value of x for which F(x) = 1/2. In case F(x) is discontinuous, the median is defined in such a way as to yield consistent results when the area is cumulated from either end of the distribution.