\begin{definition}[Definition:Addition/Sum]
Let $a + b$ denote the operation of addition on two objects $a$ and $b$.
Then the result $a + b$ is referred to as the '''sum''' of $a$ and $b$.
Note that the nature of $a$ and $b$ has deliberately been left unspecified.
They could be, for example, numbers, matrices or more complex expressions constructed from such elements.
\end{definition}