somnolence (n.)

• acedia
• apathy
• boredom
• drowsiness
• dullness
• enervation
• ennui
• fatigue
• heaviness
• hebetude
• indifference
• languor
• lassitude
• lenitude
• lethargy
• lifelessness
• listlessness
• oscitancy
• pandiculation
• passivity
• phlegm
• sleepiness
• sloth
• slothfulness
• slowness
• sluggishness
• stretching
• stupefaction
• stupor
• torpidity
• torpidness
• torpor
• weariness
• world-weariness
• yawning