Point of no return
（重定向自Equitime）
The point of no return (PONR) is the point beyond which one must continue on one's current course of action because turning back is physically impossible, prohibitively expensive, or dangerous. A particular irreversible action (e.g., setting off an explosion or signing a contract) can be a point of no return, but the point of no return can also be a calculated point during a continuous action (such as in aviation).