This paper examines the four components of sexual identity: biological sex, gender identity, social sex-role, and sexual orientation. Theories about the development of each component and how they combine and conflict to form the individual's sexual identity are discussed. As defined here, social sex-role includes the individual's femininity and masculinity. Sexual orientation includes the individual's physical and affectional sexual preferences for relationships with members of the same and/or opposite biological sex. This paper may help to clarify meanings of the following terms used in research on sexual identity; sex, gender, femininity, masculinity, heterosexuality, and homosexuality.