Read the excerpt from "Mother Tongue."

Lately, I’ve been giving more thought to the kind of English my mother speaks. Like others, I have described it to people as “broken” or “fractured” English. But I wince when I say that. It has always bothered me that I can think of no other way to describe it other than “broken,” as if it were damaged and needed to be fixed, as if it lacked a certain wholeness and soundness.

How does Tan build a central idea of her story in the excerpt?