Bisexuality is a romantic attraction, sexual attraction, or sexual behaviour toward both males and females, or romantic or sexual attraction to people of any sex or gender identity; this latter aspect is sometimes alternatively termed pansexuality.
The term bisexuality is mainly used in the context of human attraction to denote romantic or sexual feelings toward both men and women, and the concept 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.
Bisexuality has been observed in various human societies and elsewhere in the animal kingdom throughout recorded history. The term bisexuality, however, like the terms hetero- and homosexuality, was coined in the 19th century.