Reference #356: Thinking in Systems
In a nonlinear system, a change does not produce an effect of proportionate size. For example, the average speed of cars on a freeway is affected only slightly by an increase in the density of traffic. However, at some point a small increase in car density leads to a rapid decrease in average speed — a traffic jam is formed.
Non-linearities change the relative strength of feedback loops. They are the chief cause of the shifting dominance in loops that categorise many systems.
Meadows. Thinking in Systems, 2008. (91-92)