"Vacuum is space void of matter. The word stems from the Latin adjective vacuus for \"vacant\" or \"void\". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often discuss ideal test results that would occur in a perfect vacuum, which they sometimes simply call \"vacuum\" or free space, and use the term partial vacuum to refer to an actual imperfect vacuum as one might have in a laboratory or in space."@en . . . . .