The term bisexuality is mainly used for people that have both heterosexual and homosexual attraction.[1][2][9] Bisexuality is one of the three main classifications of sexual orientation along with heterosexuality and homosexuality, all of which exist on the heterosexual–homosexual continuum. A bisexual identity does not necessarily equate to equal sexual attraction to both sexes; commonly, people who have a distinct but not exclusive sexual preference for one sex over the other also identify themselves as bisexual.[10]
Scientists do not know the exact determinants of sexual orientation, but they theorize that it is caused by a complex interplay of genetic, hormonal, and environmental influences,[11][12][13] and do not view it as a choice.[11][12][14] Although no single theory on the cause of sexual orientation has yet gained widespread support, scientists favor biologically based theories.[11] There is considerably more evidence supporting nonsocial, biological causes of sexual orientation than social ones, especially for males.[3][9][15]
Bisexuality has been observed in various human societies,[16] as well as elsewhere in the animal kingdom,[17][18][19] throughout recorded history. The term bisexuality, like the terms hetero- and homosexuality, was coined in the 19th century by Charles Gilbert Chaddock.[20][21]
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^Carroll JL (2015). Sexuality Now: Embracing Diversity. Cengage Learning. p. 322. ISBN978-1305446038. Archived from the original on 7 November 2021. Retrieved 8 March 2019. Pansexuality is also sometimes included under the definition of bisexuality, since pansexuality rejects the gender binary and encompasses romantic or sexual attractions to all gender identities.
^Rice, Kim (2009). "Pansexuality". In Marshall Cavendish Corporation (ed.). Sex and Society. Vol. 2. Marshall Cavendish. p. 593. ISBN978-0-7614-7905-5. Archived from the original on 13 November 2020. Retrieved 3 October 2012. In some contexts, the term pansexuality is used interchangeably with bisexuality, which refers to attraction to individuals of both sexes... Those who identify as bisexual feel that gender, biological sex, and sexual orientation should not be a focal point in potential relationships.
^Soble, Alan (2006). "Bisexuality". Sex from Plato to Paglia: a philosophical encyclopedia. Vol. 1. Greenwood Publishing Group. p. 115. ISBN978-0-313-32686-8. Some bisexuals' attractions, however, appear to be gender 'blind'; that is, they are attracted to individuals independently of their sex- and gender linked attributes ... People with a gender-blind or 'pansexual' orientation are open not only to relations with men and women as traditionally figured in our society but also to relations with individuals who identify themselves as some combination of man/woman or some alternative gender entirely.
^ abLamanna, Mary Ann; Riedmann, Agnes; Stewart, Susan D (2014). Marriages, Families, and Relationships: Making Choices in a Diverse Society. Cengage Learning. p. 82. ISBN978-1-305-17689-8. Archived from the original on 30 November 2016. Retrieved 11 February 2016. The reason some individuals develop a gay sexual identity has not been definitively established – nor do we yet understand the development of heterosexuality. The American Psychological Association (APA) takes the position that a variety of factors impact a person's sexuality. The most recent literature from the APA says that sexual orientation is not a choice that can be changed at will, and that sexual orientation is most likely the result of a complex interaction of environmental, cognitive and biological factors...is shaped at an early age...[and evidence suggests] biological, including genetic or inborn hormonal factors, play a significant role in a person's sexuality (American Psychological Association 2010).
^Harper, Douglas (November 2001). "Bisexuality". Online Etymology Dictionary. Archived from the original on 26 October 2004. Retrieved 16 February 2007.