\begin{definition}[Definition:Rational Line Segment]
A '''rational line segment''' is a line segment the square of whose length is a rational number of units of area.
In other words, a '''rational line segment''' is a line segment whose length belongs to the set $\left\{{x \in \R_{>0} : x^2 \in \Q}\right\}$.
{{EuclidSaid}}
: ''{{:Definition:Euclid's Definitions - Book X/3 - Rational Line Segment}}''
{{EuclidDefRefNocat|X|3|Rational Line Segment}}
\end{definition}