Spacer

A spacer is generally something used to create a space between two objects, often to properly position them.

There are also a number of specialised usages for the term.

* Rebar spacers or reinforcement bars spacers are linear or point proucts manufactured of plastic, concrete or more rarely metal, used to provide the correct cover (distance from formwork) for the reinforcement steel bars in concrete constructions.
* Asthma spacers are used to ensure proper delivery of inhaled asthma medication.
* Orthodontic spacer
* Spacers, the first humans to emigrate to space in Isaac Asimov's Robot Series, also used in certain other sci-fi franchises to designate a being who resides primarily aboard ships and stations in space
* in space opera, and science fiction and roleplaying games in general, the word is often used to refer to humans in general or a specific caste of humans who live in outer space, or (by analogy with "sailor") serve as the crew of spaceships.
* molecular spacers on a molecular level
* In the High Guard, the military force of the Systems Commonwealth (from the series "Gene Roddenberry's Andromeda"), a Spacer is a junior enlisted rating in the Argosy (space navy). It is equivalent to a Crewman in "Star Trek"'s Starfleet, or a seaman in the present-day United States Navy.