g has 23 distinct synonyms spread across 8 of its 9 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a metric unit of weight equal to one thousandth of a kilogram
one of the four nucleotides used in building DNA; all four nucleotides have a common phosphate group and a sugar (ribose)
the cardinal number that is the product of 10 and 100
a unit of force equal to the force exerted by gravity; used to indicate the force to which a body is subjected when it is accelerated
a unit of information equal to 1000 megabytes or 10^9 (1,000,000,000) bytes
a unit of information equal to 1024 mebibytes or 2^30 (1,073,741,824) bytes
(physics) the universal constant relating force to mass and distance in Newton's law of gravitation
Synonyms, antonyms and the broader and narrower relations for g come from Princeton University’s WordNet. Full sources and licences.