SPEED – a buzz word in today’s scenario, is a measure of “how fast”. Everybody is in a rat race and wants to run at the fastest speed. ‘Speed’ is used in variety of contexts and is measured using variety of methods in their own contexts.According to physics, speed is related to motion. Distance travelled by a moving body in a given time is called speed. Other related terms are angular speed, velocity, and angular velocity. Angular speed is the angular distance per unit time. (Linear) Velocity and angular velocity are vector quantities and are defined as displacement (linear/angular) per unit time.Speed is measured using different kinds of sensors operating on different principles. Subsequent sections will discuss various kinds of sensors used for measurement of speed (and related vector quantity, velocity).