synergy
Concise Oxford English Dictionary © 2008 Oxford University Press:
synergy /ˈsɪnədʒi/ (also synergism)
▶noun interaction or cooperation of two or more organizations, substances, or other agents to produce a combined effect greater than the sum of their separate effects.
– derivatives
synergetic adjective,
synergic adjective.
synergetic adjective,
synergic adjective.
– origin C19: from Gk sunergos ‘working together’.
'synergy' also found in these Oxford entries:

