What term is used to describe a significant reduction in energy within a system?

The term that describes a significant reduction in energy within a system is "Depletion." Depletion refers to the exhausting or diminishing of a resource or energy supply within a system, which can occur due to overuse, consumption, or the draining of available energy sources. This concept is widely applicable in various scientific contexts, including ecology, geology, and energy studies, where it signifies that the system’s ability to sustain energy levels is compromised.

In contrast, conservation refers to the careful management of resources to prevent depletion, while enrichment involves increasing the quantity or quality of resources. Accumulation suggests a buildup of resources or energy rather than a reduction. Thus, depletion is the most accurate term for a significant reduction in energy within a system.