PERPENDICULAR LINES -
Two straight lines are called perpendicular lines if they intersect at right angle (90 degrees). In other words, if you have two lines, and they meet in such a way that the angle formed between them is 90 degrees, then those lines are said to be perpendicular.
Here's a graphical representation:
In the adjoining diagram ∠BOC = a right angle. So the lines AB & CD are perpendicular to each other. Usually it is written as AB ⊥ CD. Here notice that each of ∠BOC, ∠AOC, ∠AOD, or ∠BOD is a right angle.
Perpendicular Bisector Of A Line Segment -
A line is called a perpendicular bisector of a line segment if it bisects the line segment and is perpendicular to it.
In the adjoining diagram, M is the mid point of the line segment AB and ∠BMC = 90⁰. So, the line CD is the perpendicular bisector of the line segment AB.