Denotes gravity in mathematical notation.

Specifically, g is the acceleration due to the local gravitational field – the force exerted by the Earth on a sky diver in free fall, for example.

The sky diver experienced a force of 5 g. (not "5 g's")

g is measured in metres per second per second (m/s²) and has a value of 9.81 m/s² on Earth.

Not to be confused with G.