In human sexuality, a bisexual or bi person (more rarely, pansexual) can be sexually attracted, sexually active, and/or in love with people of either sex. Note that the attraction to both sexes is not always equal; a bisexual can be more attracted to people of one sex than the other. Other sexual orientations are homosexuality and heterosexuality. As homosexuality often is seen as a graver social stigma, "bisexual" might be used as a euphemism for persons who haven't publicly announced themselves as homosexual. The opposite of bisexual is monosexual.
Pansexuality is a neologism that expresses essentially the same concept as bisexuality. The difference is that it refers to someone who is attracted to all sexes/genders, rather than both sexes. It is used mainly by people who wish to express their understanding and acceptance of transgenderism or recognizing the existance of the intersex genders. Pansexuality can include an attraction for less mainstream forms of sexuality, principally BDSM.
Trysexual is a neologism and a pun on bisexual. It is used as a humorous term for someone who will try any sexual experience at least once.
Incidence of bisexuality
Some studies, notably Sexual Behavior in the Human Male (1948) and Sexual Behavior in the Human Female (1953) by Dr. Alfred C. Kinsey, note that when asked to rate themselves on a continuum from completely heterosexual to completely homosexual, and when the individual's behavior as well as their identity is analyzed, the majority of people appear to be at least somewhat bisexual. Most people have some attraction to either sex, although usually one sex is preferred. According to Kinsey, therefore, only a minority (5-10%) can be considered to be fully heterosexual or homosexual. Conversely, an even smaller minority can be considered "fully" bisexual, if that term is defined as having no preference for one sex over another.
Because bisexuals sometimes do not feel like they fit into the gay community at large, and because bisexuals have a tendency to become invisible in public (fitting in rather seamlessly into both homosexual and heterosexual society), some are committed to forming their own communities and movement. In an effort to create both more visibility, and a symbol for the bisexual community to gather behind, Michael Page created the bisexual pride flag.
Biphobia is a neologism that describes either the view that people are either heterosexual or homosexual, or that bisexuals are "contaminated." Bisexuals may also be victimised by the more common homophobia.
Bisexuality has a militaristic heritage. Examples include most people who had homosexual relationships in Ancient Greece since most also had wives. Perhaps the most famous and militaristic example is Alexander the Great who had many wives, but also a sexual relationship with his close friend Hephaestion.
Ancient Sparta also encouraged homosexual relationships among their troops so long as the men also had wifes and produced children. The Spartans thought that physical relationships between military men would solidify combat loyalty and encourage heroic tactics in the defense of their lover. It is not known the extent that this played in Sparta's military success but they were regarded as the premier fighting force of their day.