> For the complete documentation index, see [llms.txt](https://mandober.gitbook.io/math-debrief/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mandober.gitbook.io/math-debrief/200-set-theory/set-relations/basic-set-relations.md).

# Basic set relations

* the empty sets vs non-empty sets

Sets are necessarily *containers* since non-empty sets contain objects. The only set that contains no objects is the empty set.