Asexuality is a non-existent or extremely low level of sexual attraction or interest in sexual activity. It can be considered a lack of sexual orientation, an alternative to heterosexuality, an alternative to homosexuality, or an alternative to bisexuality.
Alfred Kinsey was one of the first researchers to recognize asexuality. When he found he could not accurately record the sexual attraction of some individuals on his Kinsey scale, he instead used a category called "X" to group individuals with "no socio-sexual contacts or reactions."
Asexuality is sometimes called nonsexuality.