Definition: Thymine is a pyrimidine base (nitrogenous base) and constituent of nucleotides and as such one member of the base pair A-T (adenine-thymine) in DNA.

Thymine, also known as 5-methyluracil, is a pyrimidine nucleobase. It is found in the nucleic acid DNA. In RNA thymine is replaced with uracil in most cases. In DNA, thymine(T) binds to adenine (A) via two hydrogen bonds to assist in stabilizing the nucleic acid structures.

Thymine combined with deoxyribose creates the nucleoside deoxythymidine, which is synonymous with the term thymidine. Thymidine can be phosphorylated with one, two or three phosphoric acid groups, creating respectively TMP, TDP or TTP (thymidine mono- di- or triphosphate).

See also

 pyrimidine nucleobase (nucleobases)
 DNA