Sexual intercourse, or coitus or copulation, is chiefly 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; also 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 vulva or vagina (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, most commonly 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 among the sexual acts contributing to human bonding and 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.