Definition:Medial

Definition
A medial is a strictly positive real number which is the mean proportional between two rational line segments which are commensurable in square only.

Thus a number $a \in \R_{>0}$ is medial iff $a$ is of the form:


 * $a = \rho \sqrt [4] k$

where:
 * $\rho$ is a rational number
 * $k$ is a rational number whose square root is irrational.