International Encyclopedia of Systems and Cybernetics

"Whatever the system produces and sends back into its environment" (B. BANATHY, 1988, p.87).

Outputs can be of matter, energy or information.

Matter emitted has generally been transformed, either upgraded or downgraded. Energy is normally downgraded by the system, which uses it to activate its internal processes. Information is mostly upgraded or even directly created within the system.

Any output has a destination into the environment whether fuzzy or precise.

The whole or parts of the environment act as sinks for the system outputs. It is very important to know to which extent the environment is able to accomodate itself as a sink, for, once crossed a critical threshold, the system may well suffocate in its own products, be it pollutants, over-production of some item, or over-population, for example. This imply the need to study the rate of production of every significant output, in order to be able to define optima and bearable maxima.

It should be noted that many systems produce some types of outputs while being unaware of it, bringing about some unsuspected side-effects, as for a recent example, the ozone hole produced by chlorinated propellents.

Outputs must cross boundaries or interfaces. The way they do it in space and time is also a very important feature of the interrelation between the system and its environment.

Finally, the previous convenient conditioning of the output within the system is of utmost importance in relation to the acceptance by the environment and the reactions of the latter towards the system.