Cell death is defined as the biological process which ceases the function of the cell to carry out. This can be caused due to the formation of new cells in place of old cells.
Or it can be cause due to some serious disease or may be caused due to the injury or due to the death of that organism to which these cells belong.
And another case is that when X-ray photon interact with the human cell while it passes through the cell, it will damage the cell and cease it to function well and a more drastic condition occurs and that cell become dead.
