lassitude (n.)

• acedia
• adynamia
• anemia
• apathy
• atony
• blues
• boredom
• cachexia
• cachexy
• cowardice
• debilitation
• debility
• depression
• disinterest
• disregard
• doldrums
• drowsiness
• dullness
• dumps
• enervation
• enfeeblement
• ennui
• etiolation
• exhaustion
• eyestrain
• faintness
• fatigue
• feebleness
• flabbiness
• flaccidity
• heaviness
• hebetude
• heedlessness
• impotence
• indifference
• insouciance
• languor
• lenitude
• lethargy
• lifelessness
• listlessness
• oscitancy
• overstrain
• passivity
• phlegm
• powerlessness
• prostration
• sleep
• sleepiness
• sloth
• slothfulness
• slowness
• sluggishness
• slumber
• softness
• somnolence
• strain
• stupefaction
• stupor
• tedium
• tiredness
• torpidity
• torpidness
• torpor
• unconcern
• unmindfulness
• weakness
• weariness
• world-weariness