The Collaborative International Dictionary of English v.0.48:

Coexistence \Co`ex*ist"ence\, n.
   Existence at the same time with another; -- contemporary
   existence.
   [1913 Webster]

         Without the help, or so much as the coexistence, of any
         condition.                               --Jer. Taylor.
   [1913 Webster]

WordNet (r) 3.0 (2006):

coexistence
    n 1: existing peacefully together

Moby Thesaurus II by Grady Ward, 1.0:

57 Moby Thesaurus words for "coexistence":
   Eisenhower Doctrine, Monroe Doctrine, Nixon Doctrine,
   Truman Doctrine, accompaniment, agreement, appeasement,
   balance of power, brinkmanship, coetaneity, coetaneousness,
   coevalneity, coevalness, coincidence, colonialism, compromise,
   concomitance, concurrence, containment, contemporaneity,
   contemporaneousness, detente, deterrence, diplomacy, diplomatic,
   diplomatics, dollar diplomacy, dollar imperialism, expansionism,
   foreign affairs, foreign policy, good-neighbor policy, imperialism,
   internationalism, isochronism, isolationism, manifest destiny,
   militarism, nationalism, neocolonialism, neutralism, nonresistance,
   open door, open-door policy, peace offensive, peaceful coexistence,
   preparedness, shirt-sleeve diplomacy, shuttle diplomacy,
   simultaneity, spheres of influence, synchronism, synchronization,
   the big stick, tough policy, unison, world politics