Vacuum

优选词，正式主题词

1. A 'Physical' with no 'Massive' parts. (EMMO). 2. vacuum, space in which there is no matter or in which the pressure is so low that any particles in the space do not affect any processes being carried on there. (Brittanica). 3. A space from which (almost) all air or other gas has been removed (Cambridge Dictionary). 4. A vacuum is space devoid of matter. (Wikipedia)