Sexual intercourse, also known as copulation or coitus, commonly refers to the act in which a male's penis

Penis

The penis is a biological feature of male animals including both vertebrates and invertebrates...

 enters a female's vagina

Vagina

The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...

 for the purposes of sexual pleasure or reproduction. The entities may be of opposite sex

Sex

In biology, sex is a process of combining and mixing genetic traits, often resulting in the specialization of organisms into a male or female variety . Sexual reproduction involves combining specialized cells to form offspring that inherit traits from both parents...

es, or they may be hermaphroditic

Hermaphrodite

In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...

, as is the case with snail

Snail

Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...

s. The term may also describe other sexual penetrative

Sexual penetration

Sexual penetration is a sexual activity that involves the entry into a bodily orifice, such as the vagina, anus or mouth, with a body part or an object....

 acts, such as anal sex

Anal sex

Anal sex is the sex act in which the penis is inserted into the anus of a sexual partner. The term can also include other sexual acts involving the anus, including pegging, anilingus , fingering, and object insertion.Common misconception describes anal sex as practiced almost exclusively by gay men...

, oral sex

Oral sex

Oral sex is sexual activity involving the stimulation of the genitalia of a sex partner by the use of the mouth, tongue, teeth or throat. Cunnilingus refers to oral sex performed on females while fellatio refer to oral sex performed on males. Anilingus refers to oral stimulation of a person's anus...

 and fingering

Fingering (sexual act)

Fingering is the manual manipulation of the clitoris, vulva, vagina, or anus for the purpose of sexual arousal and stimulation. It may constitute the entire sexual encounter or it may be part of mutual masturbation, foreplay or other sexual activities. To "finger oneself" is to masturbate in this...

, which can be practiced by both heterosexual

Heterosexuality

Heterosexuality is romantic or sexual attraction or behavior between members of the opposite sex or gender. As a sexual orientation, heterosexuality refers to "an enduring pattern of or disposition to experience sexual, affectional, physical or romantic attractions to persons of the opposite sex";...

 and same-sex

Homosexuality

Homosexuality is romantic or sexual attraction or behavior between members of the same sex or gender. As a sexual orientation, homosexuality refers to "an enduring pattern of or disposition to experience sexual, affectional, or romantic attractions" primarily or exclusively to people of the same...

 partners.

Sexual intercourse typically plays a powerful role in human bonding

Human bonding

Human bonding is the process of development of a close, interpersonal relationship. It most commonly takes place between family members or friends, but can also develop among groups such as sporting teams and whenever people spend time together...

, often being used solely for pleasure and leading to stronger emotional bonds.