A lesbian is a homosexual woman or girl.: 48  The word is also used for women in relation to their sexual identity or sexual behavior, regardless of sexual orientation, or as an adjective to characterize or associate nouns with female homosexuality or same-sex attraction.: 22  Relatively little in history was documented to describe female homosexuality, though the earliest mentions date to at least the 500s BC. When early sexologists in the late 19th century began to categorize and describe homosexual behavior, hampered by a lack of knowledge about homosexuality or women's sexuality, they distinguished lesbians as women who did not adhere to female gender roles. They classified them as mentally ill—a designation which has been reversed since the late 20th century in the global scientific community. Women in homosexual relationships in Europe and the United States responded to the discrimination and repression either by hiding their personal lives, or accepting the label of outcast and creating a subculture and identity. Following World War II, during a period of social repression when governments actively persecuted homosexuals, women developed networks to socialize with and educate each other. Gaining greater economic and social freedom allowed them to determine how they could form relationships and families. With second-wave feminism and the growth of scholarship in women's history and sexuality in the late 20th century, the definition of lesbian broadened, leading to debate about the term's use. Lisa M. Diamond found that female same-sex sexuality is uniquely fluid even over short time spans but that lesbians display a more stable or core same-sex orientation. Some women identify as simultaneously lesbian and bisexual. One's sexual identity is not necessarily the same as one's sexual behavior. For example, lesbians may remain closeted and identify as straight in order to avoid homophobic discrimination. Source: Wikipedia (en)