# What is *acceleration*?

**Acceleration**is the rate of change of the velocity of an object with respect to time. It is therefore a vector quantity, just like velocity. Meaning that it includes both a magnitude (size) and a direction.

## Input

**Millimeters Per Square Second**is an acceleration unit equal to 1/1000 of a meter per square second.

## Output

**Meters Per Square Second**is the base unit of acceleration in the International System of Units (SI).