Bisexuality
Bisexuality is a romantic or sexual attraction or behavior toward both males and females (gender binary), to more than one gender, or to both people of the same gender and different genders. It may also be defined to include romantic or sexual attraction to people regardless of their sex or gender identity, which is also known as pansexuality.

The term bisexuality is mainly used for people that have both heterosexual and homosexual attraction. 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.

Scientists do not know the exact cause of sexual orientation, but they theorize that it is caused by a complex interplay of genetic, hormonal, and environmental influences, and do not view it as a choice. Although no single theory on the cause of sexual orientation has yet gained widespread support, scientists favor biologically based theories. There is considerably more evidence supporting nonsocial, biological causes of sexual orientation than social ones, especially for males.

Bisexuality has been observed in various human societies, as well as elsewhere in the animal kingdom, throughout recorded history. The term bisexuality, like the terms hetero- and homosexuality, was coined in the 19th century by Charles Gilbert Chaddock.
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