the quality or state of being mortal
"The mortality of humans makes us acutely aware of our finite lives."
the ratio of deaths in an area to the population of that area; expressed per 1000 per year
"The city's annual mortality rate was recorded at eight deaths per thousand residents."
The state or quality of being mortal.
"The mortality rates in that region have dropped significantly over the last decade due to better healthcare."
The state of being susceptible to death.
"The high mortality rate among unvaccinated children highlighted their increased susceptibility to death from preventable diseases."
In plain English: Mortality is the fact that all living things eventually die.
"The high mortality rate from the flu was a major concern for doctors this winter."
Usage: Mortality refers specifically to the rate at which people die in a particular population rather than an individual's susceptibility to death, so use it when discussing statistics like infant mortality instead of personal fate. Avoid confusing this term with "mortal," which describes something capable of dying or extremely unpleasant.
The word mortality comes from the Old French mortalite and ultimately derives from the Latin words for "death." It entered English with its current meaning of being subject to dying, reflecting its original sense of relating directly to death.