Exhaustion is a state of being incredibly tired. Running a marathon on a hot day often results in exhaustion.
Your exhaustion might be due to physical fatigue, after shoveling snow for hours or chasing after your runaway dog, or mental tiredness. A terrible argument with your best friend can lead to exhaustion, for example. Another kind of exhaustion is caused by illness or general weakness. Exhaustion comes from the verb exhaust, "a drawing off," specifically of strength. from the Latin exhaurire, "draw off" or "take away."