SYNCHRONY
synchronism, synchrony, synchronicity, synchroneity, synchronization, synchronisation, synchronizing
(noun) the relation that exists when things occur at the same time; “the drug produces an increased synchrony of the brain waves”
Source: WordNet® 3.1
Etymology
Noun
synchrony (countable and uncountable, plural synchronies)
synchronicity, the state of two or more events occurring at the same time.
Source: Wiktionary
Syn"chro*ny, n.
Definition: The concurrence of events in time; synchronism. [R.]
Geological contemporaneity is the same as chronological synchrony.
Huxley.
Source: Webster’s Unabridged Dictionary 1913 Edition