Sexual Intercourse

Male and Female Genital During Sexual Intercourse: Magnetic Resonance Image (MRI) of a male and female engaged in sexual intercourse, sagittal view. The uterus and vaginal canal are colored brown and the penis and testicles are colored pink. In this frame the penis has reentered the vagina, and the glans of the penis is pushing the posterior wall of the vaginal canal up to the cervix and uterus. The erect penis bends and flexes upward as it penetrates far up into the vaginal canal. Swelling and tightening occur in the outer vaginal walls, while the inner two thirds expand slightly; the uterus becomes elevated. In combination with vaginal moistening, these actions work together to accommodate and seize the thrusting penis - all in preparation for receiving sperm.

Sexual intercourse, also known as coitus or copulation, is principally the insertion and thrusting of a male's penis, usually when erect, into a female's vagina for the purposes of sexual pleasure or reproduction, or both. This is additionally known as vaginal intercourse or vaginal sex. Other forms of penetrative sexual intercourse include penetration of the anus by the penis (anal sex), penetration of the mouth by the penis or oral penetration of the female genitalia (oral sex), sexual penetration by the fingers (fingering), and penetration by use of a strap-on dildo. These activities involve physical intimacy between two or more individuals and are usually used among humans solely for physical or emotional pleasure and commonly contribute to human bonding.

A variety of views concern what constitutes sexual intercourse or other sexual activity, which can also impact views on sexual health. Although the term sexual intercourse, particularly the variant coitus, generally denotes penile-vaginal penetration and the possibility of creating offspring (which is the fertilization process known as reproduction), it also commonly denotes penetrative oral sex and particularly penile-anal sex. Non-penetrative sex acts, such as non-penetrative forms of cunnilingus or mutual masturbation, have been termed outercourse, but may additionally be considered sexual intercourse. The term sex, often a shorthand for sexual intercourse, can mean any form of sexual activity. Because people can be at risk of contracting sexually transmitted infections during these activities, though the transmission risk is significantly reduced during non-penetrative sex, safe sex practices are advised.


Reproductive sexual intercourse between non-human animals is more often termed copulation, and sperm may be introduced into the female's reproductive tract in non-vaginal ways among the animals, such as by cloacal copulation. For most non-human mammals, mating and copulation occur at the point of estrus (the most fertile period of time in the female's reproductive cycle), which increases the chances of successful impregnation. However, bonobos, dolphins and chimpanzees are known to engage in sexual intercourse regardless of whether or not the female is in estrus, and to engage in sex acts with same-sex partners. Like humans engaging in sexual activity primarily for pleasure, this behavior in the aforementioned animals is also presumed to be for pleasure, and a contributing factor to strengthening their social bonds.
