state of being mortal 不免一死. 
(also mor`tality rate) number of deaths in a specified period of time 死亡率: Infant mortality (ie The rate at which babies die) was 20 deaths per thousand live births in 1986. 1986年的婴儿死亡率为生育成活率的千分之二十. 
large number of deaths caused by a disease, disaster, etc （疾病﹑ 灾难等造成的）大量死亡.# mor`tality table (esp in insurance) table showing how long people at various ages may normally be expected to live （尤指保险业的）死亡率表.