C
cross-boundary flows the transport of materials or information across a given physical boundary.

E
embodied energy the total energy required to produce a good or service, including both direct and indirect uses of energy.

entropy a measure of the unavailable energy in a system; according to the second law of thermodynamics entropy increases in all physical processes.

F
first law of thermodynamics the physical law stating that matter and energy cannot be created or destroyed, only transformed.

I
industrial ecology the application of ecological principles to the management of industrial activity.

input-output analysis (static and dynamic) a modeling approach that determines the physical or economic relationships between sectors of an economy; a static analysis does not account for changes in technology and capital stock, but a dynamic model does account for these changes.

M
methodological pluralism the view that a more comprehensive understanding of problems can be obtained by using a combination of perspectives rather than just one perspective.

S
second law of thermodynamics the physical law stating that all physical processes lead to a decrease in available energy, that is, an increase in entropy.

solar flux the continual flow of solar energy to the earth.

system boundary a boundary defining an area for study, such as a wetland or urban area; used in economic/ecological modeling.