"median" is referenced in the pages listed below.

Definiton and properties of a trapezoid (coordinate geometry) including altitude and median
Trapezoid median (midline or midsegment) definition and properties
Definition and properties of medians of a triangle
Median of a triangle construction with compass and straightedge or ruler. A triangle has three medians. They are lines linking each vertex to the midpoint of the opposite side. We first find the midpoint, then draw the median. A Euclidean construction.