WordNet (r) 3.0 (2006):

continuum
    n 1: a continuous nonspatial whole or extent or succession in
         which no part or portion is distinct or distinguishable
         from adjacent parts

Moby Thesaurus II by Grady Ward, 1.0:

82 Moby Thesaurus words for "continuum":
   Indian file, acreage, area, array, articulation, bank, breadth,
   buzz, catena, catenation, chain, chain reaction, chaining,
   concatenation, connection, consecution, course, cycle, descent,
   dimension, drone, emptiness, empty space, endless belt,
   endless round, expanse, expansion, extension, extent, field, file,
   filiation, galactic space, gamut, gradation, hum, infinite space,
   interstellar space, line, lineage, measure, monotone, nexus,
   nothingness, outer space, pendulum, periodicity, plenum,
   powder train, progression, proportion, queue, range, rank,
   recurrence, reticulation, rotation, round, routine, row, run,
   scale, sequence, series, single file, space, spatial extension,
   spectrum, sphere, spread, string, succession,
   superficial extension, surface, swath, thread, tier, tract, train,
   void, volume, windrow