Chapter (noun)

1. A main division of a book or treatise.
2. A branch of an organization, especially a religious or fraternal organization.

Origin:

From middle english chapitre, from old french chapitre, from latin capītulum, from caput ("head"), as each chapter was a separate heading.

Examples:

1. She was reading a chapter in her history book.
2. The first chapter of the novel sets the scene for the story.
3. The local chapter of the American Red Cross is hosting a blood drive.
4. The chapter in the textbook covered the history of the Roman Empire.
5. The new chapter in the organization will focus on environmental activism.