acceleration

$\textit{Acceleration}$ is the (instantaneous) rate of change of velocity. Acceleration may be either linear acceleration, or angular acceleration. It is a vector quantity with dimension $length/time^{2}$ for linear acceleration, or in the case of angular acceleration, with dimension $angle/time^{2}$. $$$$ In SI units, linear acceleration is measured in $meters/second^{2}$ ($m \cdot s^{-2}$), and angular acceleration is measured in $radians/second^{2}$. $$$$ In physics, any increase or decrease in speed is referred to as acceleration and similarly, motion in a circle at constant speed is also an acceleration, since the direction component of the velocity is changing.