Answer:
Velocity
Step-by-step explanation:
The change of velocity rate it's the definition of acceleration.
While increasing or decreasing velocity, it means that an acceleration it's happening.
Using some math:
![a=(dv)/(dt)](https://img.qammunity.org/2020/formulas/engineering/college/milvn3hs3agmnqjxewhtrz14i1td3s69q7.png)
This can be read as "the acceleration it's equal to te variation of velocity with respect to time"