Perpendicular Bisector = Mediatriz

A PERPENDICULAR BISECTOR (=mediatriz) is a perpendicular line that divides a segment in two equal parts. 

Una MEDIATRIZ (=perpendicular bisector) es una línea perpendicular que divide un segmento en dos partes iguales.

And to review how to draw the perpendicular bisector of a given segment, have a look at the animation they have at mathopenref.com