\begin{definition}[Definition:Edgeless Graph]
An '''edgeless graph''' is a graph with no edges.
That is, an '''edgeless graph''' is a graph of size zero.
Equivalently, an '''edgeless graph''' is a graph whose vertices are all isolated.
The '''edgeless graph''' of order $n$ is denoted $N_n$ and can be referred to as the '''$n$-edgeless graph'''.
\end{definition}