Tan build a central idea of her story in the excerpt by:
Tan discusses her mother’s use of English to build the idea that a form of language can be purposeful and meaningful even if it is nonstandard.
In the excerpt Tan wrote about how her mother's english is nonstandard and that is why she has described it to others as "broken or fractured." Nevertheless, she is bothered by the fact that she cannot use another word so that it does not come across as if her mother's english needed fixing. More than the use of words to describe her mother's english. Tan is aiming to highlight that non-standard english is still valuable and should not be looked-down.