Well, number one is on the inside of the DNA molecule we have these bases that are able to form hydrogen bonds. So we have one base that interacts with a complementary base on the other single strand molecule and that forms our hydrogen bond. So in this case, this is hydrogen bonding and this is also hydrogen bonding. So we can say hydrogen bonding and this is also hydrogen bonding or simply age bonding. Okay? So a base on one DNA strand interacts with via hydrogen bonds with a complementary base on the other DNA molecule.