This document defines key concepts related to health, illness, and disease. It explains that health involves complete physical, mental and social well-being, while illness is a unique personal response and disease is a pathological change in the body. Illnesses can be acute or chronic. The five stages of illness are also outlined: symptom experience, assumption of a sick role, medical care contact, dependent client role, and recovery. Basic human needs and factors affecting health are discussed, including Maslow's hierarchy of needs. Risk factors for illness and general health maintenance activities are also listed.