countably subadditive

countably subadditive

[kau̇nt·ə·blē səb′ad·əd·iv]
(mathematics)
A set function m is countably subadditive if, given any sequence of sets, the measure of the union is less than or equal to the sum of the measures of the sets.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.