
Sadness is being part of human, a natural reaction from a painful circumstances. All of us will experience some point in our lives. It is a transient feelings that passes as a person comes to term with his troubles.He/she feels bad, but continues to cope with living.
While depression is a physical illness with many symptoms than an unhappy mood. It can linger for weeks, months or even years. He/she may feel overwhelmed & hopeless.