vinculum

Vinculum is a term used in various disciplines, derived from the Latin vinculum meaning "bond" or "tie." In mathematics and related fields, a vinculum denotes a horizontal bar that binds together a sequence of symbols. It is most familiar in decimal notation, where an overbar over a repeating block indicates that the block repeats indefinitely, as in 0.\overline{3} = 0.333... or 0.\overline{142857} = 0.142857142857... The same symbol can also be used to group terms or to indicate the entire portion of an expression to which a radical or other operator applies in some notational traditions, serving a role similar to parentheses.

In anatomy, vinculum refers to a narrow band or ligament that connects or binds structures. The term is used in multiple anatomical contexts, for example the vincula tendinum, which are small fibrous bands that suspend flexor tendons to the bones of the fingers, helping to supply blood and stabilize the tendons. In biology and botany, similar bands may be described as vincula in certain organs or tissues.

The concept appears in historical and linguistic usage as well, though in modern mathematics the overline remains the most common representation. The plural form vincula is used when referring to multiple such bars or bands.