Beam expanders are optical devices that take a collimated beam of light and expand its width (or, used in reverse, reduce its width).

A volume expander is a type of intravenous therapy that has the function of providing volume for the circulatory system.

Fluids increasing blood volume intravenously.

a proprietary, freeware, closed source, decompression software utility developed by Allume Systems (a subsidiary of Smith Micro Software formerly known as Aladdin Systems).

(dentistry) A device used to widen the upper jaw so that the bottom and upper teeth will fit together better.

A port expander is computer hardware that allows more than one device to connect to a single port on a computer.

In graph theory, an expander graph is a sparse graph that has strong connectivity properties, quantified using vertex, edge or spectral expansion.

palatal expander