结,联系,括线
Vinculum \Vin"cu*lum\, n.; pl. L. {Vincula}, E. {Vinculums}.
[L., from vincire, vinctum, to bind.]
1. A bond of union; a tie.
2. (Math.) A straight, horizontal mark placed over two or
more members of a compound quantity, which are to be
subjected to the same operation, as in the expression
x^{2} + y^{2} - vinc{x + y}.