What is the difference between mourn and grieve ?Feel free to just provide example sentences.

'mourn' is sadder, heavier, quieter, more weighed down by the loss. It is that quieter, aching sense of loss. Like a part of you is missing now. It is feeling deeply sad for something that was lost or gone. It is longing. It is a quiet feeling where you miss something that is lost forever.

'grieve' is more painful. It can be a little more chaotic or erratic, unpredictable because people show grief in different ways. "grieving" can feel like the heart is breaking, ripping into pieces inside. It is intense and strange and painful. It is a more violent type of sad, a more broken kind. Grief can make people feel almost any emotional extreme: angry, destructive, crying, unhappy laughter, reckless and impulsive, shut down and catatonic, or even just numb. Grieving can also mean you go from one emotional extreme and then switch to a different emotional extreme. So it can be very dramatic and extreme and unpredictable. Grief makes people do strange things sometimes, before they recover.