Amy Tan's essay "Mother Tongue" is a wonderful tale that addresses the substance of languages and how language is not only a tool of communication, but a sociological tool of measuring individual worth.
Amy Tan says that she has come to realize that something unusual goes on with language—at least her own, based upon the Chinese her mother grew up speaking, the English her mother uses as her "second language," Amy's use of this special version of her mother's English, and her own perception that her mother's English was somehow "broken"—at least this is how Ms. Tan used to feel.
The author notes that the language her mother speaks is very different than "American English," but that it is deceiving in that her mother understands more than one might think when listening to her speak.
You should know that my mother's expressive command of English belies how much she actually understands. She reads the Forbes report, listens to Wall Street Week, converses daily with her stockbroker, reads all of Shirley MacLaine's books with ease—all kinds of things I can't begin to understand.
When Amy Tan recalls growing up, her mother would have Amy speak on the phone, pretending to be her mother, so that people would take her more seriously. One time Amy did this with her mother's stockbroker. More recent to this story, her mother had been diagnosed with a benign brain tumor, but when she went to the doctor's office, the CAT scan was lost and no one was remotely concerned with her need to understand her prognosis—having lost a husband and son, both to brain tumors. Amy's mother refused to leave the office until someone called her daughter. When this occurred, everyone was much more cordial with Amy than with her mother: promises were made and apologies graciously extended. In both cases, the perception based on her mother's "limited" English gave people the idea that Amy's mother wasn't very bright, or worse, was not worth their time. This is the sociological aspect of language.
When Amy first decided she wanted to be a writer, she was not encouraged to do so: English was her second language, and the peculiarities of the language (which confuse native English speakers, such as analogies) often confused her. When she began to write fiction, she made a conscious decision to write to a specific audience: she decided to write to her mother; as she was writing about relationships between mothers and daughters in her stories.
It was most gratifying to Amy Tan when her mother read The Joy Luck Club, Amy's first book. Her mother gave her praise that meant a great deal to Tan:
...I knew I had succeeded where it counted when my mother finished reading my book and gave me her verdict: 'So easy to read.'
I believe that there is a play on words with the title, "Mother Tongue." It literally means one's first language. If raised in Italy, it is Italian; in France, it is French. This is not to say that people of other countries do not learn English as well, but generally there is a language specific to the place where they were born: this is their mother tongue. However, in Amy Tan's story, I believe she is making a statement about her mother's form of English: her mother's tongue. While it may be difficult for some people to understand it, it is part of who she is, and it does not reflect negatively on her mother because it is "different." She is just as special a person, despite what language she uses or how she uses it.