A crux is a textual passage that is corrupted to the point that it is difficult or impossible to interpret and resolve.
[1] Cruxes occur in a wide range of pre-modern (ancient, medieval, and Renaissance) texts, printed and manuscript.
Though widely exposed to readers and scholars, the texts of William Shakespeare's plays yield some of the most famous literary cruxes.
Editors have reached no consensus on exactly what "ropes in such a scarre" can mean, or how it should be amended: "no satisfactory explanation or emendation has been offered.
In editions of Greek and Roman authors, a crux is marked off by obeli, to indicate that the editor is not confident enough either to follow the manuscript reading or to print a conjecture.