Pronunciation: ' r ē - ˌ män-, -m ə n-
Function: noun
Date: 1914
: a definite integral defined as the limit of sums found by partitioning the interval comprising the domain of definition into subintervals, by finding the sum of products each of which consists of the width of a subinterval multiplied by the value of the function at some point in it, and by letting the maximum width of the subintervals approach zero