\begin{definition}[Definition:Euclid's Definitions - Book X (II)/4 - Fourth Binomial]
{{EuclidSaid}}
:''Again, if the square on the greater term be greater than the square on the lesser by the square on a straight line incommensurable in length with the greater, then, if the greater term be commensurable in length with the rational straight line set out, let the whole be called a '''fourth binomial''';''
{{EuclidDefRef|X (II)|4|Fourth Binomial}}
\end{definition}