1) Thymine (T) is one of four chemical bases in DNA, the other three being adenine (A), cytosine (C), and guanine (G). Within the DNA molecule, thymine bases located on one strand form chemical bonds with adenine bases on the opposite strand. The sequence of four DNA bases encodes the cell's genetic instructions.

2) A pyrimidine base (C5H6N2O2) that is one of the four bases coding genetic information in the polynucleotide chain of DNA.