Critical care units are specialized medical facilities that cater to critically ill patients who require constant and intensive medical care. Synonyms for critical care unit include intensive care unit (ICU), critical care ward, emergency care unit, and high dependency unit (HDU). The term ICU is the most commonly known synonym, and it is used interchangeably with critical care unit. Emergency care unit refers to a unit that provides immediate medical attention to patients with life-threatening conditions. The critical care ward is a hospital ward equipped to provide intensive care to critically ill patients. The HDU is a specialized unit that provides comprehensive medical care to patients who require close monitoring but do not require the level of care provided by an ICU.