How does Harper Lee use language to enhance characterization in To Kill a Mockingbird?

Harper Lee absolutely uses language to enhance
characterization in To Kill a Mockingbird. By "language" I assume
you mean the way people speak (their dialogue) in this novel.  This story takes place in
the South, so of course we would expect some southern dialect.  We get it from many
characters, but others have an entirely different way of speaking.  Those whose language
stands out include Calpurnia, Atticus, Miss Maudie, Bob Ewell, and
Scout.

Calpurnia is a puzzle, because she speaks in two
separate dialects.  For the most part, we hear Cal speak much like Atticus.  Later, we
discover that's because they were educated in a similar way and from similar
sources--the Bible and law books.  When she gets to church, though, we hear an entirely
different Calpurnia, one who speaks in the Negro dialect.  She makes that change, she
explains to Scout, because she doesn't want them to think she's "puttin' on airs."  Both
ways of speaking suit the two parts of Calpurnia's
life.

Atticus speaks in a rather formal langauge, generally
much more formal than those around him.  That comes from his early training in reading
but also from his work in the law.  This way of speaking suits him because it sets him
apart, somehow, as being an upright and educated man--one who would do what is right no
matter the cost.

Miss Maudie is a southern lady, but she
speaks her mind.  She's not one to gossip, but she's not afraid to raise her voice when
the "foot-washin' Baptists come glowering through with their condemning scriptures.  A
good contrast to Miss Maudie is Miss Stephanie, who is much less formal and mature in
her dialogue as well as her subject matter. 

Bob Ewell is
the least educated and respectful character in this group, and his dialogue reflects
that.  He's not only rude and rather cocky, but he's also woefully undereducated--as
when he mistakes appendicitis for ambidextrous in the courtroom.  His dialogue is a
perfect reflection of his character.

Scout is another whose
language matches her character.  She's sometimes irreverent and sometimes a hothead, and
her language reflects that--"Cecil Jacobs is a big wet he-en!"  When she's more
contemplative and serious, her language reflects that, as well, though she is still
young and sometimes gets it all wrong (as in the scene outside the
jailhouse).

If one were to select some passages of dialogue
for each of these characters, a reader could pretty quickly and correctly ascertain what
kind of person each one of them is, it seems to me.  This novel is an excellent example
of dialogue used to create and enhance character.