G vs purine

G and purine both are nouns.

Word	Noun	Adjective	Verb	Adverb
G	Yes	No	No	No
purine	Yes	No	No	No

As nouns, purine is a hypernym of G; that is, purine is a word with a broader meaning than G:

G (noun)	purine (noun)
the 7th letter of the Roman alphabet	a colorless crystalline organic base containing nitrogen; the parent compound of various biologically important substances
the cardinal number that is the product of 10 and 100	any of several bases that are derivatives of purine
a unit of information equal to 1024 mebibytes or 2^30 (1,073,741,824) bytes
a unit of information equal to 1000 megabytes or 10^9 (1,000,000,000) bytes
(physics) the universal constant relating force to mass and distance in Newton's law of gravitation
one of the four nucleotides used in building DNA, also known as deoxyguanylate, or dGMP; all four nucleotides have a common phosphate group and a sugar (ribose)
a purine base found in DNA and RNA; pairs with cytosine