From The Art and Popular Culture Encyclopedia
Heterosexuality is sexual or romantic attraction between opposite sexes, and is the most common sexual orientation among humans. The current use of the term has its roots in the broader 19th century tradition of personality taxonomy. These continue to influence the development of the modern concept of sexual orientation, gaining associations with romantic love and identity in addition to its original, exclusively sexual meaning.
The adjective heterosexual is used for intimate relationships and/or sexual relations between male and female individuals, who may or may not identify themselves as straight. Heterosexuality, as an identifier, is usually contrasted with homosexuality and bisexuality. The term straight is used predominantly to refer to self-identified heterosexuals of either sex. Unlike lesbian, there is no gender-specific term that is only used for self-identified heterosexual females.