crux
/krʌks/noun
(pl. cruxes 或cruces /ˈkruːsiːz/)(the crux)
1- the decisive or most important point at issue症结, 关键：
the crux of the matter is that attitudes have changed.
问题的关键是态度已经改变了。
1.1
- a particular point of difficulty难点, 难题：
both cruces can be resolved by a consideration of the manuscripts.
两个难题都可以通过考虑原稿得以解决。
词源
mid 17th cent. （denoting a representation of a cross, chiefly in crux ansata 'ankh', literally 'cross with a handle'）： from Latin, literally 'cross'.