Simplify the following text for a Grade 3 native English-speaking person.
Original: Physicists often discuss ideal test results that would occur in a perfect vacuum , which they simply call `` vacuum '' or `` free space '' , and use the term partial vacuum to refer to real vacuum . The Latin term in vacuo is also used to describe an object as being in what would otherwise be a vacuum .
Simplified: Sometimes it is just called a vacuum .