【記】casual偶然，ty踢︰偶然一踢給踢死了→嚴重傷亡事故

casualty n.嚴重傷亡事故＝accident；事故中的傷亡者，受害者，失蹤者
【例】The enemy suffered casualties. 敵人遭受傷亡。

口訣：因為漫不經心casual 而導致的傷亡

Causal 踢，你隨意踢東西很容易造成災禍、死傷人數

Mortality is more about the death rate or the concept of death.
Casualty includes both injuries and deaths.
Fatality refers strictly to deaths.