The state of being sad, unhappy, sorrowful, or mournful.
Examples:
1. "I was deeply saddened by the death of my grandfather."
2. "The sadness showed on the faces of the bushfire victims, after their home was burnt to cinders."

Sadness is also known as a negative emotion. Some of the obvious signs of sadness on some ones faces are:

• The corners of the lips droop, and the bottom lip may tremble
• The inner corners of the eyebrows are drawn upwards

Others are:

• The skin below their eyelids will become triangulated
• The corners of the skin below their eyelids will become raised.