(1) In an organization synergy is the ability of a group to outperform even its best individual member. (Buchanan and Huczynski,1997).
(2) A construct or collection of different elements working together to produce results not obtainable by any of the elements alone. The elements, or parts, can include people, hardware, software, facilities, policies, documents: all things required to produce system-level results. (Blanchard 2004).
(1) Buchanan, D. and A. Huczynski. 1997. Organizational behavior, introductory text, 3rd edition, p. 276. Upper Saddle River, NJ, USA: Prentice Hall.
(2) Blanchard, B. 2004. System Engineering Management, p. 8. Hoboken, N, USAJ: John Wiley.
Synergy is two or more things functioning together to produce a result not independently obtainable. The term synergy comes from the Greek word synergia meaning "working together". It is often used in business or other human activitiy systems to describe outcomes which can only be achieved by encouraging people or organizations to work together, often through encouraging friction or creative tensions between them. In medicine synergy is used to describe combinations of drugs which interact in ways that enhance or magnify one or more effects, or side-effects, of those drugs. This may give both positive and negative effects.
Definition (2) is typical of the use of the term synergy in systems engineering texts to describe how system behavior emerges from the interaction between elements. In this sense synergy is closely related to emergence.