for pleasure, this behavior in these animals is also presumed to be for pleasure, and a contributing factor to strengthening their social bonds. Behaviors Definitions Sexual intercourse may be called coitus, copulation, coition, or intercourse. Coitus is derived from the Latin word coitio or coire, meaning "a coming together or joining together" or "to go together", and is known under different ancient Latin names for a variety of sexual activities, but usually denotes penile–vaginal penetration. This is often called vaginal intercourse or vaginal sex. Vaginal sex, and less often vaginal intercourse, may also denote any vaginal sexual activity, particularly if penetrative, including sexual activity between lesbian couples. Copulation, by contrast, more often denotes the mating process, especially for non-human animals; it can mean a variety of sexual activities between opposite-sex or same-sex pairings, but generally means the sexually reproductive act of transferring sperm from a male to a female or sexual procreation between a man and a woman. Although sex and "having sex" also most commonly denote penile–vaginal intercourse, sex can be significantly broad in its meaning and may cover any penetrative or non-penetrative sexual activity between two or more people. The World Health Organization (WHO) states that non-English languages and cultures use different words for sexual activity, "with slightly different meanings". Various vulgarisms, slang, and euphemisms are used for sexual intercourse or other sexual activity, such as fuck, shag, and the phrase "sleep together". The laws of some countries use the euphemism "carnal knowledge". Penetration of the vagina by the erect penis is additionally known as intromission, or by the Latin name immissio penis (Latin for "insertion of the penis"). The age of first sexual intercourse is called sexarche. Vaginal, anal and oral sex are recognized as sexual intercourse more often than other sexual behaviors. Sexual activity that does not involve penile-vaginal sex or other sexual penetration might be used to retain virginity (sometimes called "technical virginity)" or labeled "outercourse". One reason virginity loss is often based on penile–vaginal intercourse is because heterosexual couples may engage in anal or oral sex as a way of being sexually active while maintaining that they are virgins since they have not engaged in the reproductive act of coitus. Some gay men consider frotting or oral sex as a way of maintaining their virginities, with penile-anal penetration used as sexual intercourse and for virginity loss, while other gay men may consider frotting or