Any of a class of organic heterocyclic compounds, composed of fused pyrimidine and imidazole rings, that constitute one of the two groups of organic nitrogenous bases (the other being the pyrimidines) and are components of nucleic acids.
User Defined Definitions
"any of several bases that are derivatives of purine"
"a colorless crystalline organic base containing nitrogen; the parent compound of various biologically important substances"