# Definition:Rationally Expressible Number

## Definition

A number is rationally expressible if its square is rational.

Thus, the set of the rationally expressible numbers is $\set {x \in \R : x^2 \in \Q}$.

## Notes

This page uses terminologies invented by $\mathsf{Pr} \infty \mathsf{fWiki}$, which are not expected to be seen outside $\mathsf{Pr} \infty \mathsf{fWiki}$, namely: rationally expressible.