In many people, sexual orientation is clearly defined from puberty through adulthood; however, for others, sexual preferences develop and change throughout life. Many experts believe that having sexual or romantic feelings toward a person of the same sex, or even having a sexual experience involving a person of the same sex, does not necessarily mean that a person is homosexual or bisexual.
It is very common for people, especially adolescents and young adults to experiment with sexuality and with a variety of sexual behaviors. Sometimes it can take several years for a person to determine and accept his or her sexuality. In a person who is gay, this process often is called "coming out of the closet" or simply, "coming out."
A person who is homosexual may have a sexual relationship with a person of the same gender, may have sexual experiences with a person of the opposite gender (i.e., heterosexual experiences), or may not have a sexual relationship. A sexually mature adult who does not have a sexual relationship is referred to as celibate. Homosexuals, as well as heterosexuals, may have a sexual relationship with one person (i.e., a monogamous relationship), with more than one person (i.e., polygamous relationships), or may not have sex.
The term transgender is used to refer to a person who adopts characteristics that are not commonly associated with his or her gender, or to a person who changes or alters his or her gender. People who are transgender include those who dress and wear accessories (e.g., shoes, jewelry) in a manner usually associated with the opposite sex (called transvestites).
Transgender also includes those who feel that they are or should be the other gender or transition to the opposite sex via medical treatment (e.g., hormone therapy) and/or surgery (called transsexuals). A transgender person may be straight, gay, bisexual, or celibate since sexual preference is separate from sexual identity.
Because people often are reluctant to provide accurate information about their sexuality (including sexual activity and behavior and sexual orientation), and because opinions can vary regarding the definition of homosexuality (e.g., some definitions do not include people who are celibate or bisexual), it is difficult to determine the overall incidence and prevalence of homosexuality. It is estimated that approximately 5–10% of sexually mature adults are gay.
Sexual development is a complicated process and human sexuality often is affected by many factors. It is very common for sexuality and sexual orientation to change and evolve throughout a person's lifetime, beginning in early adolescence and continuing through adulthood.
Although there are several theories regarding the influence of certain factors on sexual orientation, the effect of these factors is not completely understood. Factors that may affect human sexuality include the following:
- Biological factors
- Cultural factors
- Genetic (hereditary) factors
- Environmental factors
- Moral factors
- Psychological factors
- Religious factors
- Social factors