\begin{definition}[Definition:Additive Inverse/Number]
Let $\Bbb F$ be one of the standard number systems: $\N$, $\Z$, $\Q$, $\R$, $\C$.
Let $a \in \Bbb F$ be any arbitrary number.
The '''additive inverse''' of $a$ is its inverse under addition, denoted $-a$:
:$a + \paren {-a} = 0$
\end{definition}