\begin{definition}[Definition:Linearly Irrational Number]
A number $n$ is '''linearly irrational''' if $n$ irrational but its square $n^2$ is rational.
Thus, the set of the '''linearly irrational numbers''' is:
:$\set {x \in \R \setminus \Q : x^2 \in \Q}$
\end{definition}