/ree"mahn steel"chiz, -meuhn/ , Math.
the limit, as the norm of partitions of a given interval approaches zero, of the sum of the product of the first of two functions evaluated at some point in each subinterval multiplied by the difference in functional values of the second function at the endpoints of the subinterval.
[ named after G. F. B. RIEMANN and T. J. Stieltjes ]