/ˈadnˌēn/
Noun
1. A nucleobase (a purine derivative) with a variety of roles in biochemistry including cellular respiration, in the form of both the energy-rich adenosine triphosphate (ATP) and the cofactors nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD), and protein synthesis, as a chemical component of DNA and RNA.[2] The shape of adenine is complementary to either thymine in DNA or uracil in RNA. (wikipedia.org)
2. (Biochemistry)
A nitrogenous base, one member of the basepair A-T (adenine-thymine). (biology-online.org)
3. (Biochemistry)
Purine base found in DNA paired with thymine, in RNA paired with uracil. Adenine is one of the bases that form part of a nucleotide, the structures that are present in DNA chains. (biology-online.org)
4. A purine base, C5H5N5, one of the fundamental components of nucleic acids, as DNA, in which it forms a base pair with thymine, and RNA, in which it pairs with uracil. Symbol: A (dictionary.reference.com)