Sildenafil.org

Sexual intercourse

Sexual intercourse, also known as copulation or coitus, commonly refers to the act in which the male reproductive organ enters the female reproductive tract. The two entities may be of opposite sexes or not, or they may be hermaphroditic, as is the case with snails. In recent years, penetration of non-sexual organs (oral intercourse, anal intercourse) or by non-sexual organs (fingering, fisting) are also sometimes included in this definition. Traditionally, intercourse has been viewed as the natural endpoint of all sexual contact between a man and a woman.

Non-penetrative sexual contacts and mutual masturbation (oral sex may or may not be penetrative) have been referred to as "outercourse". The word sex, in the context of sexual intimacy, is often, if not universally, understood to include any mutual genital stimulation, i.e. both intercourse and outercourse.

Sexual intercourse for most animals other than humans occurs 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 even when the female is not in estrus, and to engage in sex acts with same-sex partners. In most instances, humans have sex primarily for pleasure. This behavior in the above mentioned animals is also presumed to be for pleasure, which in turn strengthens social bonds.

Text from Wikipedia.org - Available under CreativeCommons license