The child of a deaf person is not necessarily deaf. Whether a deaf person has a deaf child or not depends on its own causative factors. It is generally said that there are two types of deafness: one is congenital deafness and the other is acquired deafness. There are two types of congenital deafness: one is caused by environmental factors such as X-rays, viral infections, and teratogenic drugs taken by pregnant women in early pregnancy, and this type of deafness is usually not inherited. The other type is hereditary and generally belongs to autosomal recessive inheritance and also dominant inheritance. There are three types of inheritance as follows: 1. Both parents are phenotypically normal, but both carry the deafness-causing gene, and both parents’ deafness-causing genes are passed on to the next generation, and a deaf child is born. If one parent is a carrier of the deafness gene and is not deaf, the next generation may also be a carrier of the deafness gene and is not deaf. 2. If both parents are congenitally deaf, the resulting child will be deaf and dumb, regardless of gender. This condition is not allowed to have children. 3. If one of the parents is congenitally deaf, one half of the children born may be affected children and one half may be normal children, which is projected according to the law of heredity.