In men, ejaculation is the normal physiological response to an orgasm. It consists of the expulsion of semen from the uethra. It can occur spontaneously during sleep, particularly in adolescents just entering puberty.
The inability to ejaculate is often the symptom of an underlying condition, such as the use of certain drugs, a problem with the autonomic nervous system, or an obstruction of the ejaculatory duct. Dysejaculation, a painful or uncomfortable ejaculation, can also be a symptom of an underlying disease.