The unit of acceleration named after Galileo is the gal, written with the symbol Gal. It is a centimetre–gram–second (CGS) unit equal to 1 centimetre per second squared, or 0.01 metres per second squared.
The gal is used mainly in gravimetry, the precise measurement of Earth's gravitational field. Geophysicists commonly use milligals and microgals when describing small gravity differences caused by variations in rock density, elevation, groundwater, tides, or underground magma. Standard gravity is approximately 980.665 Gal.
The name honours Galileo Galilei, whose experiments and mathematical analyses of falling bodies helped establish the study of motion and acceleration. The unit is not an SI unit, although it has historically been permitted for certain uses alongside SI. ISO standards later deprecated it, but it remains useful in geophysics and gravity surveying.
A common mix-up is confusing the unit's name with Galileo's first name or with the symbol g for acceleration due to gravity. The correct answer is Gal: “gal” is the unit name, while “Gal” is its conventional symbol.