Bisexuality is romantic attraction, sexual attraction or sexual behavior toward males and females. The term is mainly used in the context of human attraction to denote romantic or sexual feelings toward men and women. Pansexuality may or may not be subsumed under bisexuality, as the terms are often treated as synonyms and people may consider bisexuality, like pansexuality, to encompass romantic or sexual attraction to all gender identities or romantic or sexual attraction to a person irrespective of that person's biological sex or gender.
Bisexuality is one of the three main classifications of sexual orientation, along with a heterosexual and a homosexual orientation, all a part of the heterosexual–homosexual continuum. People who have a distinct but not exclusive sexual preference for one sex over the other may 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.