What is the difference between a 'complicated' and a 'complex' system?
Discussing the difference between 'complicated' and 'complex' may seem rather pedantic to many, but it is an essential differentiation in systems management.
Complicated system - A system with many interacting components where the interrelationship between those components is, within 'normal' conditions, predictable. A Boeing 747 would be considered a 'complicated system'.
Complex system - A system with many interacting components where the interrelationship between those components is, even within 'normal' conditions, unpredictable. An ecosystem would be considered a 'complex' system.
Problems also fall into the categories of 'complicated' and 'complex' for the same reason. A more classical English term for a 'complex problem' is a 'wicked problem'.
Human IQ has often been described as a measurement of an individual's ability to manage complexity. It is useful to consider this alternative; 'Human IQ is a measurement of an individual's intellectual ability to turn a 'complex' problem or system into a 'complicated' problem or system. What is viewed as a 'complex' or unpredictable system to someone with an average IQ may be a 'complicated' and predictable system to someone with genius level IQ.