"Oligospermia" is a medical term that refers to a low sperm count, which is one of the potential causes of male infertility. A low sperm count means that the semen, the fluid ejaculated during orgasm, contains fewer sperm than normal. The World Health Organization (WHO) defines a low sperm count as fewer than 15 million sperm per milliliter of semen. When you mention "nil sperm," it typically refers to a condition known as "azoospermia," where there are no sperm cells present in the ejaculate. Azoospermia can be caused by a variety of factors, including: Obstructive azoospermia: This occurs when there is a blockage in the reproductive tract that prevents sperm from being present in the ejaculate. This could be due to congenital absence of the vas deferens, prior surgeries, or infections. Non-obstructive azoospermia: This occurs when there is a problem with sperm production in the testes. Causes can include genetic conditions, hormonal imbalances, or damag...