leth·ar·gy 
(lĕthər-jē)
(lĕthər-jē)n. pl. leth·ar·gies
1.
a. A lack of energy or vigor; sluggishness.
b. A lack of interest or enthusiasm; apathy: held a pep rally to shake the students out of their lethargy.
2. Medicine An abnormal state of drowsiness, as caused by disease or drugs.
[Middle English letargie, from Old French, from Late Latin lēthārgia, from Greek lēthārgiā, from lēthārgos, forgetful : lēthē, forgetfulness + ārgos, idle (a-, without; see A-1 + ergon, work; see werg- in the Appendix of Indo-European roots).]
Synonyms: lethargy, lassitude, torpor, languor
These nouns refer to a deficiency in mental and physical alertness and activity. Lethargy is a state of sluggishness, drowsy dullness, or apathy: "Your lethargy is such that you will not fight even to protect the freedom which your mothers won for you" (Virginia Woolf).
Lassitude implies weariness or diminished energy such as might result from physical or mental strain: "His anger had evaporated; he felt nothing but utter lassitude" (John Galsworthy).
Torpor suggests the suspension of activity characteristic of an animal in hibernation: "Confinement induced torpor, and from torpor he could easily slip to passivity, resignation, death" (Larry McMurtry).
Languor is the indolence typical of one who is satiated by a life of luxury or pleasure: "with that slow, catlike way about him, cool, aloof, almost contemptuous in the languor and ease of his movements" (Tobias Wolff).
These nouns refer to a deficiency in mental and physical alertness and activity. Lethargy is a state of sluggishness, drowsy dullness, or apathy: "Your lethargy is such that you will not fight even to protect the freedom which your mothers won for you" (Virginia Woolf).
Lassitude implies weariness or diminished energy such as might result from physical or mental strain: "His anger had evaporated; he felt nothing but utter lassitude" (John Galsworthy).
Torpor suggests the suspension of activity characteristic of an animal in hibernation: "Confinement induced torpor, and from torpor he could easily slip to passivity, resignation, death" (Larry McMurtry).
Languor is the indolence typical of one who is satiated by a life of luxury or pleasure: "with that slow, catlike way about him, cool, aloof, almost contemptuous in the languor and ease of his movements" (Tobias Wolff).