In bookbinding, section (sometimes ) refers to a group of bifolios, or sheets of paper, stacked together and folded in half. The term is sometimes used interchangeably with signature, though the latter technically refers only to the signature mark at the bottom of the first page of a printed section.
The section is the basic building block of codex bindings. In Western bookbinding, sections are sewn through their folds, with the sewing thread linking each section to its neighboring sections.