The gram (abbreviation, g or gm) is the cgs (centimeter/gram/second) unit of mass. A force of one dyne (1 dyn), applied to a mass of one gram (1 g), will cause that mass to accelerate at one centimeter per second squared (1 cm/s2).
Material density, more often referred to simply...(WhatIs.com)
Mass is often specified in larger or smaller units than the gram, by changing the power-of-10 prefix multiplier. A mass of one kilogram (1 kg) is 1000 g. A mass of one milligram (1 mg) is 0.001 g. A mass of one microgram (1 µg) is 10-6 g. A mass of one nanogram (1 ng) is 10-9 g. In the International System of Units (SI), the kilogram is the preferred unit of mass.