(n.) The quality or state of being sleepy.

acedia apathy boredom brain fag debilitation debility drowsiness dullness enervation enfeeblement ennui eyestrain faintness fatigue goneness heart strain heaviness hebetude inanimation indifference jadedness lackadaisicalness languidness languishment languor languorousness lassitude lenitude lentor lethargy lifelessness listlessness mental fatigue mental strain oscitancy overstrain overtiredness passivity phlegm satedness sloth slothfulness slowness sluggishness somnolence stance fatigue strain stupefaction stupor supineness tiredness torpidity torpidness torpitude torpor weakness wearifulness weariness world-weariness