Bisexuals are men and women who achieve sexual or erotic attraction to members of both sexes. Usually, but not always, the bisexual person engages in sexual activity with partners of both sexes. Slang terms referring to bisexuals are "AC/DC" (based on the term used to describe two types of electrical current), "switch-hitters" (a baseball term describing a batter who hits from either side of home plate depending on who's pitching), or people who "swing both ways" (another baseball phrase, but may also relate to swinging as sexual behavior).

Little to No Study on Bisexual Behavior
Compared to heterosexuality and homosexuality, very little scientific study has been conducted on bisexuality. Based on the studies that have been done, it appears that bisexuals are not people whose orientation is fundamentally homosexual but who have some heterosexual sex on the side. Nor are they people whose orientation is fundamentally heterosexual but who enjoy homosexual sex on the side.

Also, fundamentally, they are not people who, at one point in their lives, engage in sexual behavior with persons of one sex and then, at another point, engage in sexual behavior with persons of the other sex, although this pattern of sequential changes is sometimes called transitional bisexuality. Rather, bisexuals are people who are sexually attracted to persons of both sexes during the same general time period in their lives.

It is thought that people develop and experience bisexuality in a number of different ways. For some it begins as a form of experimentation that adds a spark to their sex lives, but it does not become the main arena of sexual activity. For others it is a deliberate choice to participate in whatever feels best at the moment.

Criteria Conducive to Bisexual Behavior:
Three particular sets of circumstances have been thought to be conducive to bisexuality:

• Sexual experimentation in a relationship with a close friend is quite common among women and can also occur between two male friends or a male homosexual may develop a sexual relationship from a previously casual but friendly relationship with a woman.
• Group sex is another avenue for bisexual experimentation.
• Finally, some people adopt a bisexual philosophy as an outgrowth of a personal belief system. For instance, some women who have been active in the women's movement find they are drawn closer to other women by the experience and translate this closeness into sexual expression.

Men who are bisexuals are likely to experience homosexual attraction and engage in homosexual experiences before they become aware of their bisexuality. For women, on the other hand, the trend is to experience heterosexuality first.

Although persons with a bisexual orientation do not fit simply into any one mold, there are a few patterns that may apply to many bisexuals. Some men and women seem to alternate their choice of sex partners randomly, depending on availability and circumstances. Some have committed relationships in this fashion, seeking a partner of the alternative sex when the current relationship ends.