pons asinorum
/ˌæsɪˈnɔːrəm/noun
- the point at which many learners fail, especially a theory or formula that is difficult to grasp“笨人难过的桥”, “驴桥”; 初学者难懂的理论（或公式）。
词源
mid 18th cent.: Latin, literally 'bridge of asses', term taken from the fifth proposition of the first book of Euclid.