Answer: The length of a pendulum string, also known as the "length of the pendulum," is measured from the point of suspension to the middle of the bob because it is the point where the bob is in its equilibrium position.
Explanation: This position is where the force of gravity is balanced by the tension in the string and it is the point where the bob swings back and forth. Measuring the length of the pendulum from the point of suspension to the middle of the bob allows for a consistent and accurate measurement of the pendulum's period, which is the time it takes for the pendulum to swing back and forth once.