Vaginal sexual intercourse, also called coitus is the human form of copulation. While its primary evolutionary purpose is the reproduction and continued survival of the human species, it often is performed exclusively for pleasure.
Sexual intercourse is also defined as referring to any form of insertive sexual behavior, including oral sex, as well as anal intercourse. The phrase to have sex can mean any or all of these behaviors.
Coitus may be preceded by foreplay, which leads to sexual arousal of the partners, resulting in the erection of the penis and natural lubrication of the vagina.
To engage in coitus, the erect penis is inserted into the vagina and one or both of the partners move their hips to move the penis backward and forward inside the vagina to cause friction, typically without fully removing the penis. In this way, they stimulate themselves and each other, often continuing until highly pleasurable orgasm and ejaculation are achieved. Penetration by the hardened erect penis is also known as intromission, or by the Latin name immissio penis.