(1) A small, thin continuous-loop magnetic tape cartridge that has been used from time to time for data storage and specialized applications.

(2) The base unit of chip making. It is a slice taken from a salami-like silicon crystal ingot up to 12" (300mm) in diameter. The larger the wafer, the more chips produced in a single production pass, which comprises a series of photomasking, etching and implantation steps. Wafers are approximately 1/30th of an inch thick; however, the actual layers of transistors that make up the active circuitry are only a few microns deep.

Wafers started out being very small from one to three inches in diameter. Then came 100mm ingots (approximately 4"), followed by 125, 150, 200 and 300mm. Various different wafer sizes are used today, depending on the type of chip being made. See chip and wafer scale integration.