What is sad and sorrow??​

disappointment, or other misfortune suffered by oneself or others: ... Therefore in summary sadness is a state of unhappiness while sorrow is a sense of deep distress, disappointment, or sadness. Therefore it can be concluded that sorrow is a more intense form of sadness, which is the basic feeling of unhappiness

those are just the expressions and a way to tell our feelings to others

nowadays most people are sad which eventually leads them to go into depression!

bikhri bikri zulfain..ye behki behki chaal