crux

باللغة العربية: مَرْبِط الْفَرَس

1. The basic, central, or essential point or feature. · The crux of her argument was that the roadways needed repair before anything else could be accomplished.
2. The critical or transitional moment or issue, a turning point.
3. A puzzle or difficulty.
4. The hardest point of a climb.
5. A cross on a coat of arms.

الجمع cruxes