Health inequalities can be defined as differences in health status or in the distribution of health determinants between different population groups. For example, differences in mobility between elderly people and younger populations, or differences in mortality rates between people from different social classes.

It is important to distinguish between inequality in health and inequity.
Some health inequalities are attributable to biological variations or free choice, and others are attributable to the external environment and conditions mainly outside the control of the individuals concerned. In the first case it may be impossible or ethically or ideologically unacceptable to change the health determinants and so the health inequalities are unavoidable.
In the second, the uneven distribution may be unnecessary and avoidable as well as unjust and unfair, so that the resulting health inequalities also lead to inequity in health.

World Health Organization. Programmes and Projects. Health Impact Assessment. Glossary of terms used. Health Inequality and Inequity. 2012.