countably subadditive set function

countably subadditive set function

[¦kau̇n·tə·blē səb¦ad·əd·iv ′set ‚fəŋk·shən]
(mathematics)
A real-valued function defined on a class of sets such that the value of the function on the union of any sequence of sets is equal to or less than the sum of the sequence of the values of the function on the sets.