The bar in Roman Numerals is named vinculum. This bar is placed above a Roman Numeral and indicates a multiple of 1000. The Romans did not use this name for the bar, it was introduced in the Middle Ages.
VINCULUM - The bar above a roman numeral
A bar over a Roman numeral multiplies the base numeral by 1000. Example: V with a bar over it = 5000
It indicates multiplication by a thousand
The number 8000 can be represented by the Roman numeral VIII with a horizontal bar placed above it or by the Roman numeral [VIII]
The number 100,000 can be represented in Roman numerals by the Roman numeral C with a horizontal bar placed above it or by the Roman numeral [C]
VINCULUM - The bar above a roman numeral
A bar over a Roman numeral multiplies the base numeral by 1000. Example: V with a bar over it = 5000
It indicates multiplication by a thousand
The number 8000 can be represented by the Roman numeral VIII with a horizontal bar placed above it or by the Roman numeral [VIII]
The number 100,000 can be represented in Roman numerals by the Roman numeral C with a horizontal bar placed above it or by the Roman numeral [C]
bar(MMMCDLXXXV)
The Roman numeral is XVI. There should be a bar over the X to indicate 10000.
The Roman Numeral for million is a capital M with a bar over it. NOT to be confused with their numeral for thousand which is only a capital M with no bar.
bar(bar(L)MMDCCXC)MMDCX
bar(XX)MMMMCDLXVI
20,000 = XX with a bar over the top. A single bar over a Roman numeral multiplies the value of the numeral by 1000. XX = 20, XX with bar = 20,000
A bar or a line over a particular Roman numeral indicates that it is to be multiplied by a thousand.