ZPG, which stands for zero population growth, refers to the balance between the number of individuals in a population and the resources available to sustain them. There are several other terms that can be used as synonyms for ZPG, including demographic equilibrium, population stability, and population balance. These terms all describe a state where the number of births and deaths in a population are roughly equal, leading to stable growth rates over time. Other related terms include population control, which refers to deliberate efforts to limit population growth through policies such as birth control and family planning, and population decline, which occurs when the number of deaths exceeds the number of births.