Mountains envelop more than 80 percent of China’s Hunan province, leaving many villages isolated from one another. Among these jagged peaks, Nüshu was formed. Experts believe Nüshu is the only writing system in the world created and used exclusively by women. Meaning “women’s writing,” Nüshu was a way for women to communicate in feudal-society China, when women were denied educational opportunities. Nüshu gave rise to a distinct female culture in which the women were known as “sworn sisters.” Typically, groups of three or four young, unrelated women would vow lifelong friendship by writing letters, singing songs, and reciting poetry in…