In mathematics, the repeating decimal "'0.999 & "'( sometimes written with more or fewer 9s before the final ellipsis, for example as "'0.9 & "', or in a variety of other variants such as "'0 . "', "'0 . ( 9 ) "', or " " " ) denotes a real number that can be shown to be equality have been formulated with varying degrees of mathematical rigor, taking into account preferred development of the real numbers, background assumptions, historical context, and target audience.
