Pair of two nucleobases, consisting of one purine and one pyrimidine base, held together by hydrogen bonds.
Note: In deoxyribonucleic acid (DNA), guanine typically pairs with cytosine and adenine typically pairs with thymine. In ribonucleic acid (RNA), adenine typically pairs with uracil.
Source:
PAC, 2018, 90, 1121. 'Terminology of bioanalytical methods (IUPAC Recommendations 2018)' on page 1143 (https://doi.org/10.1515/pac-2016-1120)