Sexual orientation is believed to refer to "an enduring pattern of emotional, romantic, and/or sexual attractions to men, women, or both sexes." According to the American Psychological Association "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."APA California Amicus Brief Sexual orientation is usually classified according to the sex or gender of the people who are found sexually attractive, and is therefore usually discussed in terms of three categories: heterosexual, homosexual, and bisexual. "However, some people may use different labels or none at all." The most common forms exists along a continuum that ranges from exclusive heterosexuality (being sexually attracted to members of the opposite sex) to exclusive homosexuality (being sexually attracted to members of the same sex) and includes various forms of bisexuality (being sexually attracted to members of either sex).

Most definitions of sexual orientation include a psychological component, such as the direction of an individual's erotic desire, or a behavioral component, which focuses on the sex of the individual's sexual partner/s. Some definitions include both components. Some people prefer simply to follow an individual's self-definition or identity.

Some scholars of sexology, anthropology and history have argued that social categories such as heterosexual and homosexual are not universal. Different societies may consider other criteria to be more significant than sex, including the respective age of the partners, whether partners assume an active or a passive sexual role, and their social status.

Sexual identity and sexual behavior are closely related to sexual orientation, but they are distinguished, with identity referring to an individual's conception of themselves, behavior referring to actual sexual acts performed by the individual, and orientation referring to "fantasies, attachments and longings." Individuals may or may not express their sexual orientation in their behaviors. People who have a homosexual sexual orientation that does not align with their sexual identity are sometimes referred to as closeted.

Sexual identity may also be used to describe a person's perception of his or her own sex, rather than sexual orientation. The term sexual preference has a similar meaning to sexual orientation, but is more commonly used outside of scientific circles by people who believe that sexual orientation is, in whole or part, a matter of choice.Fact: date=May 2008