adenine(n = noun.substance) a - (biochemistry) purine base found in DNA and RNA; pairs with thymine in DNA and with uracil in RNA;
is a kind of purine

adenine, n. a purine derivative found in all living tissue as a component base of DNA or RNA.

Etymology:
G Adenin formed as ADENOIDS: see -INE(4)

nicotinamide adenine dinucleotide, nicotinamide adenine dinucleotide phosphate