Heterosexuality is romantic or sexual attraction or behavior between persons of opposite sex or gender in the gender binary. As a sexual orientation, heterosexuality refers to "an enduring pattern of or disposition to experience sexual, affectionate, physical or romantic attractions to persons of the opposite sex"; it also refers to "an individual’s sense of personal and social identity based on those attractions, behaviors expressing them, and membership in a community of others who share them". The term is usually applied to humans, but it is also observed in all mammals.
It is one of the three main classifications of sexual orientation, along with a bisexual and a homosexual orientation, all a part of the heterosexual–homosexual continuum (asexuality also sometimes being included as the fourth).
The word is etymologically formed by adding the combining form of Greek έτερος heteros (meaning "different" or "other") as a prefix to "sexuality".
Read more about Heterosexuality: History and Demographics, Heteronormativity, Heterosexual Ally, Religious Aspects, Symbolism