\[\left( - \frac{1}{3} \right)^{4} = \left( \frac{1}{3} \right)^{4} = \frac{1}{3^{4}} = \frac{1}{\left( 3^{2} \right)^{2}} =\]
\[= \frac{1}{(9)^{2}} = \frac{1}{81}.\]