The language that Harper Lee uses can be separated by past and present, and by voice or perspective; these distinctions also correspond to adult and child. She also distinguishes between narrative and dialogue. It is primarily within the dialogue that Lee shows divisions in small-town Alabama society, which are largely based in race and class, and the intersection of those two factors.
The adult Jean Louise Finch is the first-person narrator, who is reminiscing about important events of her childhood. One of Lee's most impressive accomplishments is in making Scout believable as a child. One way she does this is by showing that Scout is a precocious child whose above-grade reading skills have given her a large vocabulary. Some of the novel's humor derives from her arrogant belief in her intellectual superiority when she mixes up big words.
An example of Scout's adult versus child contrast occurs in chapter 13, in her conversation with her father about the reasons Aunt Alexandra is staying with them. The child justifies to herself the lie she told, that she is glad her aunt is there, and then reflects that she did not understand a word her father said. In the next paragraph, the adult emerges in her detailed description of the aunt's background and education. The adult narrator uses phrases such as "she would exercise her royal prerogative."
An example of Scout's confused vocabulary is an incident in chapter 8, when she believes she hears Miss Maudie yell the word "morphodite" (not a real word) rather than "hermaphrodite" for Jem's gender-ambiguous snowperson.
Class distinctions, as presented in dialogue, are shown in chapter 3 by the conversation between the student Burris Ewell and the teacher, Miss Caroline. Lee represents the poor, white boy as using non-standard English, with pronunciations such as "fer" instead of "for," and grammatical constructions such as "I done done" for "I have done." His constant use of "ain't" is another class marker.
The class distinctions among white people are apparent in the testimonies of Bob and Mayella Ewell in the courtroom scenes (chapters 17 and 18). Bob's non-standard grammar includes "run" rather than "ran" in the past tense, and idiomatic expressions such as describing his daughter as "'screamin' like a stuck hog….'"
The differences in race and class combined emerge most strongly when Calpurnia takes the Finch children to her church (chapter 12). This scene is one of the most difficult in the book, as Lee's representation of what today is often called African-American Vernacular English (AAVE) is filtered through her ear as an upper-class white woman. Many readers will likely be surprised or offended at Scout's description of black people's speech as "'nigger-talk,'" as the child struggles to understand why Calpurnia changes her speech patterns in this situation—what linguists call "code switching." Similarly, Jem's dismissive attitude is jarring, as he says she shouldn't talk that way "'when you know better.'" Calpurnia explains her reasons for situational use of "'white-folks' talk'" as class based, as she avoids it at home so her neighbors will not "think I was puttin' on airs."