Languor

noun

1. A state of the body or mind caused by exhaustion or disease and characterized by a languid or weary feeling; lassitude; an instance of this.

   "languor of convalescence"

2. Melancholy caused by lovesickness, sadness, etc.; an instance of this.
3. Dullness, sluggishness; lack of vigour; stagnation.
4. Listless indolence or inactivity, especially if enjoyable or relaxing; dreaminess; an instance of this.
5. Heavy humidity and stillness of the air.