Rack

A rack is a framework, shelf, or stand designed to hold, store, or display objects. It can be freestanding, wall-mounted, or integrated into machinery, and typically consists of horizontal bars or supports that create organized space for items of various sizes.

Common types include kitchen racks such as dish racks and spice racks, clothing racks, wine racks, and book or display racks used in stores. Industrial variants include pallet racks and other shelving systems used in warehouses to organize goods. In computing and data centers, a rack refers to a standardized metal enclosure used to mount servers, networking equipment, and related components; the height is measured in rack units (U), with 1U equal to 1.75 inches.

In mechanical engineering, a rack is a toothed bar that engages with a pinion gear to convert rotational motion into linear motion. This rack-and-pinion arrangement is used in steering systems, CNC machines, and various linear actuators, providing precise, controllable movement.

The word rack also appears as a verb in common phrases such as "to rack one's brains," meaning to strain mentally, and "to rack up," meaning to accumulate or achieve a growing total. Historically, the term also referred to a torture device used to stretch the body, though this usage is largely literary and antiquated.

Overall, racks serve as versatile tools for organization and motion, spanning everyday furniture, industrial storage, and mechanical systems.