How many perpendicular lines are there in a rectangle?

In a rectangle, each corner or vertex forms a right angle, which is an angle measuring 90 degrees. 

A right angle is formed when two lines are perpendicular to each other.

A rectangle has four corners, and at each corner, two lines meet to form a right angle. 

So, each of these corners has two perpendicular lines meeting to create a 90-degree angle.

Counting these pairs of perpendicular lines at each of the four corners, we find there are a total of 4 perpendicular lines in a rectangle. 

This makes a total of 4 right angles (four corners, each with a right angle formed by two perpendicular lines), but when considering the number of perpendicular lines, it's 4.

So, the correct answer is 4.