Flexibility has been defined differently in many fields of engineering, architecture, biology, economics, etc.
In the context of engineering design one can define flexibility as the ability of a system to respond to potential internal or external changes affecting its value delivery, in a timely and cost-effective manner.
Uncertainty is a key element in the definition of flexibility.
For manufacturing science eleven different classes of flexibility have been identified [Browne, 1984], [Sethi and Sethi, 1990]: These definitions yield under current conditions of the system and that no major setups are conducted or investments are made (except expansion flexibility).
But in some cases tradeoffs between two flexibility types are needed.