The speed of an object measured in an infinitely small time interval is often referred to as its instantaneous speed. Instantaneous speed represents the rate at which the object is moving at a specific instant in time.

$$v = \lim_{\Delta t \to 0} \frac{\Delta x}{\Delta t}$$

As the time interval becomes very small (approaching zero), the difference between the initial position and the final position of the object becomes extremely small. This means that the instantaneous speed provides an accurate representation of how fast the object is moving at that specific instant in time.

In contrast, average speed is calculated over a finite time interval and represents the total distance traveled divided by the total elapsed time. However, instantaneous speed captures the velocity of the object at a particular point in time, without the influence of what occurred in the past or what might happen in the future.