Infertility can be divided into absolute infertility and relative infertility. Infertility with no hope of successful treatment is called absolute infertility, and infertility with hope of successful treatment is called relative infertility. This classification is important for determining the treatment outcome and prognosis of infertility patients. Relative infertility is defined as having some fertility, but below the threshold required for pregnancy. One or both partners, due to one or more factors that prevent conception or reduce fertility, resulting in temporary infertility, still have the possibility of conception if the factor is corrected. For example, if the male partner has decreased sperm viability due to varicocele or prostatitis, and the female partner has thick cervical mucus due to cervicitis, sperm cannot pass through or ovulation is irregular, all these factors have the possibility of conception after treatment. In other words, the cause of this type of infertility is simple and there is no specific obstinate disease that impairs fertility, and fertility can be achieved with proper treatment. 30% of the infertility patients can find a clear cause and can be treated clinically effectively. 70% of the patients have no clear cause, or some of the causes found cannot be treated clinically effectively for the time being, and these patients are idiopathic infertility. Men who have a sperm density of <20×106/ml in 1 ejaculation have little possibility of active fertility, but with the development of assisted reproductive technology, the success rate of artificial pregnancy can reach about 40%, regardless of in vivo or ex vivo, as long as active sperm are found. Relatively infertile patients without treatment, if they have a normal sexual life, there are still 25% to 35% can have children, including 23% within 2 years and 10% over 2 years.