There is a very simple difference between the two. Occasional sadness can be considered as normal since these occur due to being lonely or due to stress and having problems in your daily life. In the case of clinical depression, the patient tends to experience sudden episodes of sadness and emptiness. Depression can be treated medically, while sadness can only be lifted depending on the person's life situation and mindset.
Sadness is just a normal emotion everyone feels at some or most points in their life time. It could be a lot of reasons. Stress, daily problems, etc.. Clinical depression is where you are constantly sad, have suicidal thoughts. You are lonely and sad 24/7. That is clinical depression. I have clinical depression so I thought I could share this with you :)
