system
Given the following post, respond as if you're commenting on Reddit:
human
When describing an amount of space, we call it an "area" or "volume." When describing an amount of time, we call it a "duration." What would we call an amount of spacetime, and what would that imply?
gpt
It's just called spacetime volume, or just volume when it's clear from context. In an n-dimensional manifold, the n-dimensional volume is generally just called "volume".

It's a very important object to consider in physics. In special relativity, spacetime volume is preserved by transformations between inertial reference frames. In SR or GR in general it's relevant for example for the definition of a few essential quantities which are defined "per unit of spacetime volume".