ICU is a department in a hospital that gives special, close treatment to people who are very sick or badly injured. The letters stand for Intensive Care Unit: intensive here means strong, constant care, with extra watching. Patients often have machines helping them breathe or tracking the heart. Families speak of someone being ‘in ICU’ as a serious, frightening place — not a normal ward where you might sit up and chat. Doctors and nurses there are trained for emergencies and for bodies that may fail quickly. Say the three letters: I-C-U. In English it is almost always written in capitals.

加護病房（台灣也常直接說 ICU）