What does the term 'mortality' refer to?

The term 'mortality' specifically refers to the number of deaths occurring within a specific population over a defined period of time. It is often expressed in terms of mortality rate, which quantifies the frequency of deaths relative to a population, typically per 1,000 individuals in a year. This definition captures the essence of mortality as a statistical measure of the health of a population, often used in public health and epidemiological studies.

Other options present related concepts but do not capture the definition of mortality. The rate of illness and disease pertains to morbidity, which is distinct from mortality. Life expectancy at birth is a statistical measure that projects the average lifespan of individuals and is related to but not synonymous with mortality. The rate of hospital admissions reflects healthcare utilization rather than mortality itself. Thus, the correct answer encompasses the specific meaning of mortality, making it a fundamental concept in health studies and statistics.