(redirected from semen concentration)
Also found in: Dictionary, Thesaurus, Medical.
Note: This page may contain terms or definitions that are offensive or inappropriate for some readers.


1. the thick whitish fluid containing spermatozoa that is ejaculated from the male genital tract
2. another name for sperm



a thick, viscid, opalescent, and whitish fluid ejaculated during copulation by human males and males of other animal species. Constituents of semen are spermatozoa and seminal fluid.

Semen contains proteins (including enzymes and nucleopro-teins), lipids, carbohydrates, vitamins, prostaglandins, sodium salts, potassium salts, calcium salts, and other organic and inorganic substances. Semen production commences during puberty, reaches its peak at maturity, and diminishes toward old age. The quantity discharged varies from species to species. Men ejaculate 2–6 milliliters (ml), bulls an average of 4–5 ml, stallions 60–100 ml, boars as much as 250 ml, and rams 1–1.5 ml.

The potency of semen depends on the quality and quantity of spermatozoa. The quantity of spermatozoa in animal semen varies, totaling approximately 30 percent in rams, approximately 14 percent in bulls, and approximately 7–8 percent in boars and stallions. It may even vary in the same animal, depending on the animal’s conditions of existence. Seasonal secretion of semen is characteristic of most invertebrates and some vertebrates, including fish, amphibians, reptiles, and many birds and mammals. Some diseases are characterized by semen lacking (azoospermia) or deficient in spermatozoa (oligospermia) or by semen with spermatozoa that are motionless (necrospermia) or malformed (teratospermia).

Semen analyses are used in forensic medicine and in determining the causes of sterility. In agriculture, an appraisal of the quality of semen is important for the artificial insemination of farm animals, as are the methods used for diluting, storing, and transporting the semen.



The fluid that carries the male germ cells. Also known as seminal fluid.