Birth, old age, illness and death are inevitable. However, due to the unknowability of death, people always avoid it and try to avoid the word "death" in the expression of death. Although ancient books have different classifications of human death: "The emperor died and said that he would collapse; The warlord said that he would die, and the doctor said that he would die; The scholar said that he was not rich, and Shu Ren said that he would die. " But ordinary people also deny death, so they call "death" death, death, death, old age, death and so on.