heaviness vs languor

heaviness

• The state of being heavy; weight, weightiness, force of impact or gravity. 

languor

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

• Dullness, sluggishness; lack of vigour; stagnation. 

• Listless indolence or inactivity, especially if enjoyable or relaxing; dreaminess; (countable) an instance of this. 

• Heavy humidity and stillness of the air. 

• Melancholy caused by lovesickness, sadness, etc.; (countable) an instance of this. 

• To languish.