Fundamental Units:

* Meters per second (m/s): This is the standard unit of velocity in the International System of Units (SI).

* Kilometers per hour (km/h): Commonly used for road speeds and in some countries.

* Feet per second (ft/s): Used in some engineering and physics contexts, especially in the United States.

* Miles per hour (mph): Commonly used for road speeds in the United States and some other countries.

Other Units:

* Knots (kn): Used for speeds of ships and aircraft, 1 knot is approximately 1 nautical mile per hour.

* Mach: Represents the ratio of an object's speed to the speed of sound. Mach 1 is the speed of sound.

* C (speed of light): Used for extremely high speeds, such as those of light or other electromagnetic radiation.

Key Point: Velocity is a vector quantity, meaning it has both magnitude (speed) and direction. Therefore, units of velocity must indicate both speed and direction. For example, "10 m/s to the east" represents a velocity.

Let me know if you would like more information on any of these units or on velocity in general!