鞍点（Saddle point）在微分方程中，沿着某一方向是稳定的，另一条方向是不稳定的奇点，叫做鞍点。在泛函中，既不是极大值点也不是极小值点的临界点，叫做鞍点。-The saddle point (point Saddle) in the differential equation, along a certain direction is stable, and the other direction is not stable singular point, called the saddle point. In the functional, it is not the maximum value of the point, it is not the critical point, called the saddle point.