The Emergency Severity Index (ESI) is a triage system used in emergency departments to prioritize patient care based on the severity of their condition. It categorizes patients into five levels, with Level 1 being the most critical and requiring immediate attention, while Level 5 represents non-urgent cases. This system helps healthcare providers allocate resources effectively and ensure that those in greatest need receive timely treatment. Developed by the American College of Emergency Physicians, the ESI is designed to improve patient flow and reduce wait times in emergency settings. By assessing factors such as vital signs, chief complaints, and the need for immediate interventions, the ESI aids in making informed decisions about patient care and resource management.