The fair allocation of resources or treatments among different individuals or groups, such that they each get what they are owed or what they are entitled to.
Other definition: The use of resource allocation rules based on the distributive justice principle. However, the latter involves various concepts that define these rules more precisely (merit, social value, the greater good, equal opportunity, equal treatment, priority to the most disadvantaged, standard gamble, etc.).
Note: Vertical equity means that the people in the greatest need of services receive the most services, and horizontal equity means that people who have similar needs receive similar services.