But what *IS* the internet?

It's the largest equivalence class in the reflexive transitive symmetric closure of the relationship "can be reached by an IP packet from"
— Seth Breidbart
http://www.ietf.org/mail-archive/web/ietf/current/msg13884.html

via https://www.kill-9.it/blog/index.php/2018/01/17/the-internet/