Amy and Jo are foils for each other. Amy is graceful, self-conscious, and feminine. She can also be a bit snooty and self-centered. In Chapter 1, Meg describes Amy as follows:
"As for you, Amy," continued Meg, "you are altogether too particular and prim. Your airs are funny now, but you'll grow up an affected little goose, if you don't take care. I like your nice manners and refined ways of speaking, when you don't try to be elegant. But your absurd words are as bad as Jo's slang."
Unlike Amy, Jo is loud, bold, and tomboyish. She prefers to wear trousers over dresses and initially dreads the idea of marriage. In Chapter 1, Beth responds to Jo's lamentations about womanhood by saying:
"Poor Jo! It's too bad, but it can't be helped. So you must try to be contented with making your name boyish, and playing brother to us girls."
Because they are so different, Amy and Jo often quarrel. The conflict between them (when Amy burns Jo's notebooks) reflects the opposition of their characters and their lack of mutual understanding. However, a harrowing accident reminds Jo to cherish her sister, and familial love triumphs over their differences.
It is also important to note that much of the sisters' characterization happens in dialogue, so the girls shape the reader's understanding of each other. This allows the reader to become familiar both with the girls themselves and with the intimacy between the sisters.