7. EPIDEMIOLOGY The study of the distribution and determinants of health related states and events in specified population and application of this study to control the health problems

8. INCIDENCE The rate of occurrence of new cases in a defined population in a certain period of time.

9. PREVALENCE The prevalence of a health-related state in a statistical population is defined as the total number of cases of the risk factor in the population at a given time, or the total number of cases in the population, divided by the number of individuals in the population. It is used as an estimate of how common a disease is within a population over a certain period of time.

10. Risk factors A risk factor is any attribute, characteristic or exposure of an individual that increases the likelihood of developing a disease or injury. Some examples of the more important risk factors are obesity, high blood pressure, tobacco and alcohol consumption and unsafe water, sanitation and hygiene.