vinculum

‖n.; pl. L. Vincula E. Vinculums [ L., from vincire, vinctum, to bind. ] 1. A bond of union; a tie. [ 1913 Webster ]

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 x2 + y2 - x + y. [ 1913 Webster ]

3. (Anat.) A band or bundle of fibers; a fraenum. [ 1913 Webster ]

4. (Zool.) A commissure uniting the two main tendons in the foot of certain birds. [ 1913 Webster ]