Vinculum

Part of speech: noun

Pronunciation: /ˈvɪŋ.kjə.ləm/

Definitions

1. A horizontal line used in mathematics to group symbols or indicate repeating decimals ; a bond or tie that connects or unites separate elements
2. A bar placed above numbers or letters to show they should be considered together or to mark a repeating decimal pattern ; any kind of connection or link that holds things together
3. A line over mathematical expressions to indicate that they form a group or that the decimal repeats ; a connection or bond that joins parts into a unified whole

Etymology: Before it named a line in an equation, "vinculum" was a Latin word for a bond or fetter, something that physically tied one thing to another. The Romans built it from "vincire," meaning to bind or tie, plus the diminutive-style ending "-ulum," which turns an action into a small, concrete instrument. A vinculum was thus literally a little tie, the sort of cord or chain that held things together. English borrowed the word in its Latin form, keeping the sense of a connecting link. Its mathematical use is the one most readers meet, where a horizontal bar drawn above a group of terms shows that they belong together, as in the bar over a repeating decimal. The metaphorical sense of a bond or tie that unites separate elements is the older link to the original Latin meaning, so the mathematical symbol is a visual version of the same idea: a line that binds several things into one unit.