What term describes a region that contains no matter?

A vacuum is defined as a region that is devoid of matter, meaning it has no particles, air, or any physical substances within it. This concept is important in physics and various scientific fields because vacuums can affect the behavior of light, sound, and other waves, as well as chemical reactions and physical processes.

While the other terms like void, space, and gap may imply an absence of something, they do not specifically denote a complete absence of matter. For example, a void might suggest emptiness but can still have some residual particles, while space often refers to the expanse that can contain matter and energy. A gap typically indicates a break or separation in something, which does not necessarily imply the total lack of matter. Thus, vacuum is the most precise term to describe a region with no matter at all.