Illness severity refers to the extent to which a disease or condition affects a person's health and daily functioning. It can be measured using various criteria, including symptoms, duration, and the impact on physical and mental well-being. Healthcare professionals often assess severity to determine appropriate treatment options and necessary interventions. Factors influencing illness severity include the type of illness, the individual's overall health, and any underlying conditions. For example, a chronic illness may have varying severity levels, affecting how a person manages their symptoms and quality of life. Understanding severity helps in planning effective care and support.