Evolution based on an S-curve

This is probably the most important and useful pattern of evolution, which has already become a part of universal engineering knowledge and is widely used in many domains. This pattern can be described thus  

An engineering system evolves following the S-curve pattern. Its evolution begins with birth and ends with death and goes through stages of childhood, growth, maturity, and decline. 

The concept of the S-curve will be explained in general terms. We will consider here a relationship (a function) between a dependent variable, called simply variable, and an independent variable, which is in our case time. The nature of the relationship is the same for several kinds of variable. The variable may represent the performance of the system (for a car maximum speed, braking distance, fuel consumption, etc.) or its various features (e.g., weight, length, or volume). The variable may also represent the rate of change of the performance or of a feature of the system, particularly when we are interested in the dynamics of change. Finally, variable may mean the cumulative value of a specific characteristic of the system, for example, the number of patents associated with the system. 

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