The main idea of Amy Tan's "Mother Tongue" is the limitations that imperfect English can impose in society and the richness that such English can bring to writing. Tan elaborates this idea by scrutinizing her mother's language, her own use of English and society's response to different people's English usage.
The title of the essay itself is a pun: it describes both the non standard English that Tan's mother, a Chinese immigrant, uses and the native speaker's English, the "mother tongue," in which Tan herself is fluent. She opens the essay by considering her own public English, which tends to the formal and academic. She realizes this when her mother attends one of Tan's lectures. This leads to a discussion of the different "Englishes" in Tan's life. One of the most prominent is her mother's "broken English." Tan describes this English as a "language of intimacy" within the family but also notes how it diminishes status in public encounters. She tells how her stockbrokers and doctors ignored her mother's imperfect English, but responded promptly when Tan herself made the same requests in standard English. Tan then discusses how her mother's lack of English skills might have limited her in her early years, especially when it came to standardized English tests. However, the essay ends by celebrating the range of Englishes in her life. Reading an early draft of a story, Tan realizes that the English she is using is far too academic. She resolves to write using the range of English that she has used in her life, creating a vibrant story that eventually became the bestselling novel "The Joy Luck Club."