On December 30th, 2014, /u/rustbucket2010 asked the following on /r/DCcomics:
What’s the “Fourth World”? I was reading Kingdom Come and it’s mentioned.
The Fourth World is a term used both within the DC Universe to refer to a place/period of time and in ours to refer to a collection of titles written by Jack Kirby. That may sound simple but there’s a huge amount to it! As I enjoy ranting about comic book history, let’s get right down to it.