gram, g

gram is abbreviated g (no period), singular and plural:

            15 g

g is also the abbreviation for for a unit of force, no period:

            g-force

            g meter

            zero g

            1 g; 5.5 g (use g for singular and plural abbreviation of gravity; g's permitted in direct quoted speech)

but     G suit

            G-string

See also METRIC AND INTERNATIONAL MEASUREMENT.