Both parentheses, ( ), and square brackets, [ ], can also be used to denote an interval. The notation formula_10 is used to indicate an interval from a to c that is inclusive of formula_11—but exclusive of formula_12. That is, formula_13 would be the set of all real numbers between 5 and 12, including 5 but not 12. Here, the numbers may come as close as they like to 12, including 11.999 and so forth (with any finite number of 9s), but 12.0 is not included.