Monday Sept 9, 1996

What is the line called that is placed over a decimal to show that it is infintely repeating?
eg.    12.34

Hi Alice

The Oxford English Dictionary defines the word vinculum as

A straight line drawn over two or more terms, denoting that these are to be considered as subject to the same operations of multiplication, division, etc., by another term. Thus, for example, a(b + c) could be written This is the symbol that is joined to a right parenthesis to form the division bracket.

I don't know a name given to the symbol when used in the situation you describe. The straight line over the 34 in your example signifies both that the 3 and 4 are tied together but it also signifies that they are repeated. The only name that I have ever heard is "bar". I would say "We put a bar over the 34 to signify that it is repeating." I don't know of any other name for this bar and, in fact, I am not sure how to "pronounce" the number you have written in your example. "Twelve point 34 with a bar over the 34." and "Twelve point 34 with the 34 repeating." are cumbersome and "Twelve point 34, repeating." is ambiguous.


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