Butch and femme are terms used in the lesbian subculture to ascribe or acknowledge a masculine (butch) or feminine (femme) identity with its associated traits, behaviors, styles, self-perception, and so on. The terms were founded in lesbian communities in the twentieth century. This concept has been called a "way to organize sexual relationships and gender and sexual identity". Butch-femme culture is not the sole form of a lesbian dyadic system, as there are many women in butch–butch and femme–femme relationships.