Analgesia is a medical word for a state where you cannot feel pain, but you are still awake and aware. Doctors aim for this after an injury, in some operations, or with certain drugs: the pain is switched off, or turned way down, while you can still talk and think. Though actually everyday English almost never uses this noun; you will hear it in hospitals, textbooks, and among nurses. People mix it up with anaesthesia. Anaesthesia is broader: it can mean you feel nothing at all, and it often includes being put to sleep. Analgesia is narrower: it is about pain, not about sleep.

痛覺缺失、無痛覺（人還醒著，只是感覺不到痛）。