Heterosexuality

Heterosexuality is exclusive romantic or sexual desire for, or sexual activities with, persons of the opposite sex. It is overwhelmingly the most common sexual preference or orientation. Heterosexual behaviour (notably sexual intercourse) is responsible for the reproduction of most animal species, including humans.

Heterosexuality is colloquially referred to as being "straight", although that term can also mean anyone whose sexuality could be described as orthodox. For example, people who practice BDSM use the term to refer to anyone who does not.