1/5-1

The expression \( \frac{1}{5} - 1 \) can be simplified as follows:

1. Rewrite 1 as a fraction with denominator 5: \[ \frac{1}{5} - \frac{5}{5} \]

2. Subtract the numerators: \[ \frac{1 - 5}{5} = \frac{-4}{5} \]

Final answer:

\[ \boxed{\frac{-4}{5}} \]