lethargy — the quality or state of being drowsy and dull, listless and unenergetic, or indifferent and lazy; apathetic or sluggish inactivity.
weakness — the state or quality of being weak; lack of strength, firmness, vigor, or the like; feebleness.
disease — a disordered or incorrectly functioning organ, part, structure, or system of the body resulting from the effect of genetic or developmental errors, infection, poisons, nutritional deficiency or imbalance, toxicity, or unfavorable environmental factors; illness; sickness; ailment.