Opposites

Examples:

$\begin{array}{l}-999+999=0\\ \frac{1}{3}+\left(-\frac{1}{3}\right)=0\\ 1+\left(-1\right)=0\end{array}$

So, the opposite of $-999$ is $999$ ; the opposite of $\frac{1}{3}$ is $-\frac{1}{3}$ ; the opposite of $1$ is $-1$ .