(n.) A condition of the body, or mind, when its voluntary functions are performed with difficulty, and only by a strong exertion of the will; languor; debility; weariness.

acedia adynamia anemia apathy atony blah feeling bloodlessness blues boredom brain fag cachexia cachexy cowardice debilitation debility depression disinterest disregard doldrums drowsiness dullness dumps enervation enfeeblement ennui etiolation exhaustion eyestrain faintness fatigue feebleness flabbiness flaccidity goneness heart strain heaviness hebetude heedlessness impotence inanimation indifference insouciance jadedness lackadaisicalness languidness languishment languor languorousness lenitude lentor lethargy lifelessness listlessness mental fatigue mental strain oscitancy overstrain overtiredness passivity phlegm powerlessness prostration satedness sleep sleepiness sloth slothfulness slowness sluggishness slumber softness somnolence stance fatigue strain strengthlessness stupefaction stupor supineness tedium tiredness torpidity torpidness torpitude torpor unconcern unmindfulness weakliness weakness wearifulness weariness world-weariness