1. 
[syn: synchronism, synchrony, synchronicity, synchroneity, synchronization, synchronisation, synchronizing]
The Collaborative International Dictionary of English v.0.48:
Synchrony \Syn"chro*ny\, n.
   The concurrence of events in time; synchronism. [R.]
   [1913 Webster]
         Geological contemporaneity is the same as chronological
         synchrony.                               --Huxley.
   [1913 Webster]
WordNet (r) 3.0 (2006):
synchrony
    n 1: the relation that exists when things occur at the same
         time; "the drug produces an increased synchrony of the
         brain waves" [syn: synchronism, synchrony,
         synchronicity, synchroneity, synchronization,
         synchronisation, synchronizing] [ant: asynchronism,
         asynchrony, desynchronisation, desynchronization,
         desynchronizing]