(Mathematics - Calculus)

Let f be a bounded function defined on [a, b].
Let M(f, I) = sup {f(x): x in interval I}.
Let P be a finite partition such that P = {a = t0 < t1 < t2 < ... tn = b}.
The upper Darboux sum, when written as U(f, P) is the sum from k = 1 to n of M(f, [tk-1, tk]) |tk - tk-1|

See also: Darboux integral.