Third gender - some general definations and differences.

Perhaps in some contexts all may be considered members of the same “third gender” category,  but it is also useful and important to clarify some basic differences between these terms and others. Below are some very short, shorthand definitions:

Eunuch: an historic English term for a man who has been castrated to perform special social functions.
Intersexual: a term referring to people who are born with a mixture of both “male” and “female” hormonal, chromosomal, and/or genital characteristics (historically referred to as “hermaphrodite.”) (See the work of biologist Anne Fausto Sterling.)
Hijra: A term originating in South India referring to a person usually born male or intersex, but who uses female pronouns as dresses in feminine/”women’s” attire.
Transsexual: a term referring to someone who changes their sex through medical (surgical and/or hormonal) procedures.
Transgendered: a term referring to someone whose gender identity is different from the one traditionally assigned to their sex category. (People are born into sex categories of male and female; many but not all then become gendered masculine or feminine and into “men” and “women.”) Thus a transgendered person born in the female sex category may identify with the gender category “man” or “boi.” This may or may not involve surgical or hormonal alteration (in other words, it can simply be a social agreement).
Drag: a term that comes out of gay culture, involving someone temporarily “performing” a gender not usually associated with their sex (through dress, gestures, and so on). Ironic humor and extravagant campiness often involved.
Transvestite/cross-dresser: These are older terms with many meanings and histories — and often the term has been used in a derogatory fashion. In terms of practice though, “cross dressers” are often not gay, but “straight” men who simply enjoy dressing up as “women.”

These definitions are not meant to be comprehensive, but simply an entry point for those unfamiliar with these terms. There are also dozens of other terms associated with specific cultures and histories. (Readers, feel free to share other definitions, links, or references!)

Some recommended books on “third gender” related issues:

Jacobs, Sue-Ellen, Wesley Thomas, and Sabine Lang (Eds). 1997. Two-Spirit People: Native American Gender Identity, Sexuality, and Spirituality. University of Illinois Press.
Manalansan, Martin. 2003. Global Divas: Filipino Gay Men in the Diaspora. Durham, NC: Duke University Press.
Namaste, Viviane. 2000. Invisible Lives: The erasure of transsexual and transgendered people. Chicago: University of Chicago Press.
Preves, Sharon. 2003. Intersex and Identity: The Contested Self. Rutgers University Press.
Reddy, Gayatri. 2005. With Respect to Sex: Negotiating Hijra Identity in South India. Chicago: University of Chicago Press.
Stryker, Susan and Stephen Whittle, (Eds). 2006. The Transgender Studies Reader. New York: Routledge.