No sperm in semen is called azoospermia, which may be caused by many factors, including:

1. Non-obstructive azoospermia: In this case, the testis does not produce sperm, which may be caused by chromosomal abnormalities, genetic factors, drugs, radiation, chemicals and other reasons.

2. Obstructive azoospermia: In this case, the testis can produce sperm, but the sperm cannot reach the ejaculated semen, which may be caused by obstruction of vas deferens, prostatitis and seminal vesiculitis.

3. Immune azoospermia: In this case, the immune system attacks the sperm, causing the sperm to fail to mature normally or be destroyed.

4. Testicular injury: Testicular injury or infection may also lead to azoospermia.

If you find yourself or your partner suffering from azoospermia, it is recommended to seek medical advice in time, conduct relevant examinations, determine the specific reasons and seek treatment.