To determine whether the number \( 9^{-2} \) is rational or irrational, we first simplify it:
\[ 9^{-2} = \frac{1}{9^2} = \frac{1}{81} \]
The number \( \frac{1}{81} \) is a fraction where both the numerator (1) and the denominator (81) are integers. Since it can be expressed as a fraction of two integers (with the denominator not equal to zero), \( \frac{1}{81} \) is classified as a rational number.
Therefore, \( 9^{-2} \) is a rational number.