An assembly or device capable of independent operation, such as a radio receiver, cathode-ray oscilloscope, or computer subassembly that performs some inclusive operation or function.

An element of a ring with identity that has both a left inverse and a right inverse.

1. Any military element whose structure is prescribed by competent authority, such as a table of organization and equipment; specifically, part of an organization.

2. A standard of basic quantity into which an item of supply is divided, issued, or used.

A quantity adopted as a standard of measurement.