Sadness is an emotiponal pain associated with, or characterized by, feelings of disadvantage, loss, despair, grief, or lethargic, and withdraw themselves from others. An example of severe sadness is depression, a mood which can be brought on by major depressive disorder or persistent depressive disorder. Crying can be an indication of sadness.
Sadness is one of the "six basic emotions" described by Paul Ekman, along with happiness, anger, surprise, fear, and disgust. This is Broken Language.