What is Perpendicular?
Two distinct lines intersecting each other at 90° or a right angle are called perpendicular lines.
Example:
Here, AB is perpendicular to XY because AB and XY intersect each other at 90°.
NonExample:
The two lines are parallel and do not intersect each other. They can never be perpendicular to each other.  The two lines are intersecting each other at an acute angle. So, they are not perpendicular.  The lines are not intersecting each other at right angles. 
Properties of perpendicular lines

These lines always intersect at right angles.

If two lines are perpendicular to the same line, they are parallel to each other and will never intersect.

Adjacent sides of a square and a rectangle are always perpendicular to each other.

Sides of the rightangled triangle enclosing the right angle are perpendicular to each other.
Real life examples
We can observe many perpendicular lines in real life. Some examples are corner of two walls and the Red Cross symbol.
Fun Facts
