Loyalty is a point of pride, honor, and principle for Ponyboy Curtis, star player in The Outsiders. He doesn't like some of the people in his gang, especially dangerous Dallas Winston, but he would still do anything for Dallas and would defend him from danger if possible. Loyalty, according to Ponyboy, is the thread that holds his gang together. It cuts across their differences. They're loyal to each other because they know each other well, have grown up together, and have faced hard times together. In the case of the Curtis boys, their loyalty is because they are brothers, and orphaned brothers at that. The novel explores what happens when Ponyboy and his oldest brother begin to lose this loyalty for one another, under the strain of their lives.
Cherry is torn between loyalty to the Socials (and the memory of Bob) and her newfound loyalty to Ponyboy and the Greasers, yet she manages to resolve the conflict using honesty and courage.
Darry's loyalty to his brothers is founded in deep love for them.