As stated in the Explanatory at the beginning of the book, Mark Twain was very conscious of the many dialects that were in use in the part of the American South that served as a setting for Huck's adventures. The speech of the characters is written to reflect the educational level and geographical location that impacted each of those characters.
This results in many different grammatical features and uses of words in different ways by different individuals throughout the novel. Since the story is told by Huck, his dialect is the most extensively developed. "Why can't the widow get back her silver snuff-box that was stole?" His use of words, pronunciations, and combinations of singular and plural nouns and verbs, however, is quite different from Jim's markedly different speech and combinations of words into a single phrase. "I doan k'yer what de widder say, he warn't no wise man, nuther. He had some er de dad-fetchedes' ways I ever see." Other characters exhibit other unique features.