Mortality rate is the number of deaths per 1000 people
The gross mortality rate (mortality) is the number of people who die every year per 1000 people. The mortality rate gives an impression of a country's health standard. However, it is not alleszeggend: The mortality rate does not say much about the age of the people. A mortality rate is often used to describe the increase (or decrease) of a particular cause of death. You can think of the number of traffic accidents where the mortality rate is calculated over a certain period of time, and after several measures it recalculates to determine whether the measures have been useful.
Heat caused 500 extra deaths [YouTube] BkaLWoKEyBY [/youtube]