Fluid produced by the male genital tract at ejaculation. Contains spermatozoa, as well as many other substances, including those that make the ejaculate coagulate (and then called a coagulum, which is given time to liquefy before a semen analysis is done on it). Sperm cells account for only about 1 percent of the volume of the ejaculate, so it's not possible to be confident about a man's sperm count just on the basis of the volume of the semen ejaculated.

Formal name for a sperm count.

A test for detecting sperm antibodies in semen.

An absence of semen despite male orgasm; thus, different to azoospermia, an absence of sperm.

Insemination, or injection of semen or prepared spermatozoa, into the vagina, cervix, uterus (intrauterine insemination) or fallopian tube, to treat infertility. A basic form of assisted conception. The husband's (or male partner's) sperm (AIH) or donated sperm (DI) can be used.

(AIH), or assisted insemination in which the semen from the husband or male partner is used.

A complete absence of sperm (spermatozoa) in the semen. Detectable only by performing a sperm count, as semen looks the same whether it contains sperm or not. Due either to an obstruction (usually in the epididymis or vas deferens), and called obstructive azoospermia, or to failure of sperm to form or to mature in the testis (called maturation arrest). See also spermatogenesis and testicular sperm extraction (TESE).

(DI) Assisted insemination in which semen from a sperm donor (who is not the husband) is used.

(IUI) A form of assisted conception involving assisted insemination into the uterus, either for donor insemination (DI) or with husband's semen (AIH). IUI can be carried out with a woman's natural cycles or with ovarian stimulation (superovulation) using clomiphene or follicle stimulating hormone, with ovarian monitoring.

Substances, first isolated from the prostate gland's contribution to semen, now known to be universally present throughout the body, being especially produced during inflammation (when they cause pain). Drugs that stop prostaglandins being produced are used as analgesics, so called nonsteroidal anti-inflammatory drugs, or NSAIDs, which are useful also in minimising contractions of the uterus in dysmenorrhea and premature labor.

The male sex gland located just below the bladder, in front of the rectum, through which the urethra runs; it contributes secretions to the semen.

Ejaculation in which semen, instead of spurting out from the penis during male orgasm, spills upwards into the bladder. Usually has a medically important cause, which requires investigation. Treatment can be successful by isolating spermatozoa from the urine and carrying out some form of assisted conception, such as assisted insemination or in vitro fertilisation.

Male sex organs that are joined to the vas deferens on each side as they enter the prostate gland to join the urethra; once thought to act as receptacles for storing sperm, they are now known to be more important for contributing constituents of semen.

Estimation of sperm antibodies circulating in the blood. Generally not as useful as estimating semen sperm antibodies (for men) or cervical mucus sperm antibodies (for women), as these fluids have more immediate contact with sperm cells.

The result of a reaction of the immune system against sperm cells (spermatozoa) and, by limiting the ability of sperm to show motility, a contributory (or occasionally the only) cause of infertility. Can be present in serum, in cervical mucus or in semen. Can be agglutinating (which make sperm stick in clumps), immobilising (which cripple sperm particularly effectively and kill them), or coating, which interfere with sperm attachment to the zona pellucida of the egg (the secondary oocyte), preventing fertilisation. The screening test for sperm antibodies involves immunobeads.

A semen analysis, measuring the volume of the ejaculate, the density of spermatozoa ('sperm cells', or just 'sperm') in it (expressed as so many million sperm per milliliter), the proportion of sperm swimming normally (the motility), and the proportion with a normal shape. A normal sperm count consists of a volume of more than 1 ml; a density of more than 20 million per ml; a motility of more than 50 percent; and normal forms of more than 50 percent (casual examination) or more than 14 percent (critical examination by the strict criteria recently advocated by the World Health Organisation).