What is a perpendicular bisector?

We have to be a little careful here,  Everymornin17  ......for instance.....

CD divides straight angle AB into two equal right angles......but.....it's not a bisector of AB......note the difference in this pic and the one I posted above.........

Given a line segment, a perpendicular bisector is a line (or segment) that intersects the given segment at  right angles to the segment's midpoint.

Here's a pic....

AB  is the given segment.....and CD is the perpendicular bisector

BTW.....Euclid presents this easy construction in his "Elements".... it  is demonstrated here in a step-by-step fashion.....http://www.mathopenref.com/constbisectline.html

perpendicular bisector Is the segmant that devides a 180' angle into two 90s