pigeonholes

Pigeonholes are small, box-like compartments used for sorting and storing items. They can be freestanding units with many cubbies, wall-mounted slots in a cabinet, or openings in a desk or filing system. Traditionally used in offices, post rooms, libraries, and shops, pigeonholes facilitate separation and quick access to mail, documents, or small parts. The term derives from pigeon lofts or dovecotes where birds nested in many small holes; the resemblance to the many little compartments led to the metaphorical use for human-made sorting slots. Pigeonholes vary in size, material, and locking options, from simple wooden cubbies to metal filing systems with numbered slots, labels, and drawers.

In mathematics, the pigeonhole principle describes a basic counting fact: if n items are distributed among m containers with n greater than m, then at least one container must contain more than one item. The principle is simple but powerful, underpinning many proofs in combinatorics, number theory, and computer science. Common illustrations include distributing socks into drawers or placing n people into m rooms, and it applies to any finite sets and partitions. In everyday language, "pigeonholes" can also refer to categories or slots in information systems, a usage that often conveys the idea of neatly, sometimes overly, divided classifications.