There are two hydrogen bonds that exist between adenine and thymine. Adenine and thymine are two of the four nitrogen bases found in the structure of DNA. Because they only pair with each other, they are called complementary bases.
The other two complementary bases are guanine and cytosine. These four nitrogen bases make up the double strands of DNA through hydrogen bonding. Although there are only two hydrogen bonds between adenine and thymine, there are three hydrogen bond between the guanine and cytosine pairs.
Nitrogen bases are subdivided into two categories, which are the purines and pyrimidines. The pyrimidines are cytosine and thymine, while adenine and guanine are the purines.