The development of medical knowledge was a significant factor in further connotations of the term lesbian.

In the middle of the 19th century, medical writers attempted to establish ways to identify male homosexuality, which was considered a significant social problem in most Western societies.

Little of Sappho's poetry survives, but her remaining poetry reflects the topics she wrote about: women's daily lives, their relationships, and rituals.

She focused on the beauty of women and proclaimed her love for girls.

Invert described the opposite gender roles, and also the related attraction to women instead of men; since women in the Victorian period were considered unable to initiate sexual encounters, women who did so with other women were thought of as possessing masculine sexual desires.

The sexologists' claims that homosexuality was a congenital anomaly were generally well-accepted by homosexual men; it indicated that their behavior was not inspired by nor should be considered a criminal vice, as was widely acknowledged.

Women in many cultures throughout history have had sexual relations with other women, but they rarely were designated as part of a group of people based on whom they had physical relations with.

As women have generally been political minorities in Western cultures, the added medical designation of homosexuality has been cause for the development of a subcultural identity.The term lesbian is also used to express 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.The concept of "lesbian", to differentiate women with a shared sexual orientation, is a 20th-century construct.In categorizing behavior that indicated what was referred to as "inversion" by German sexologist Magnus Hirschfeld, researchers categorized what was normal sexual behavior for men and women, and therefore to what extent men and women varied from the "perfect male sexual type" and the "perfect female sexual type".Far less literature focused on female homosexual behavior than on male homosexuality, as medical professionals did not consider it a significant problem. However, sexologists Richard von Krafft-Ebing from Germany, and Britain's Havelock Ellis wrote some of the earliest and more enduring categorizations of female same-sex attraction, approaching it as a form of insanity.As a result, little in history was documented to give an accurate description of how female homosexuality is expressed.