lethargy

This term describes a heavy, oppressive lack of energy that transcends simple tiredness. It suggests a systemic slowing down of both physical movement and mental alertness, often carrying a connotation of inertia or a struggle to initiate any action. In medical contexts, it refers to a specific clinical state of drowsiness or diminished consciousness. Because it is an uncountable noun, it cannot be pluralized to describe multiple instances of the state; instead, phrases like "periods of lethargy" or "episodes of lethargy" must be used to quantify the experience.