What does 0.5 with a line on top of it mean?

The notation ( \overline{0.5} ) signifies a repeating decimal, indicating that the digit "5" repeats indefinitely. Therefore, ( \overline{0.5} ) is equivalent to the decimal 0.555..., which can also be expressed as the fraction ( \frac{5}{9} ). This notation helps to clearly denote the repeating part of the decimal.