\begin{definition}[Definition:Euclid's Definitions - Book XI/6 - Inclination of Plane]
{{EuclidSaid}}
:''The '''inclination of a plane to a plane''' is the acute angle contained by the straight lines drawn at right angles to the common section at the same point, one in each of the planes.''
{{EuclidDefRef|XI|6|Inclination of Plane}}
\end{definition}