1. Change in velocity: Acceleration is the rate of change of velocity. The greater the change in velocity over a given time, the greater the acceleration.

2. Time: Acceleration is measured over a specific time interval. The shorter the time interval for a given change in velocity, the greater the acceleration.

Let's think about it intuitively:

* Imagine two cars: Car A increases its speed from 0 to 60 mph in 5 seconds, while Car B increases its speed from 0 to 60 mph in 10 seconds. Both cars experience the same change in velocity (60 mph), but Car A has a higher acceleration because it achieves that change in a shorter time.

* Imagine a roller coaster: The acceleration you feel is greatest when the roller coaster rapidly changes its velocity (either speeding up or slowing down). The slower the change in velocity, the lower the acceleration you feel.