Bisexuality is a sexual orientation. Bisexual (sometimes shortened to bi) people are romantically or sexually attracted to both men and women.[1][2] It can also mean attraction to more than one gender.[3] Sometimes it is talked about as having romantic or sexual attraction to someone regardless of their sex or gender identity. This is also known as pansexuality.[4][1] Some bisexual people love men and women the same and some people love one more than the other. Some bisexual people have preferences to one or more sexes, however some may not.[5] A slang expression for bisexuality is "to swing both ways."
In 1948, Alfred Kinsey published the Kinsey scale. The Kinsey scale shows that sexuality is a continuum. This means it moves little by little from heterosexuality to homosexuality. On the Kinsey scale, a 0 is someone who is only heterosexual. A 6 is someone who is only homosexual. Someone who is equally homosexual and heterosexual (bisexual) is a 3.
In biology, bisexual can define an organism that has both male and female organs. This mostly refers to plants.