world was any planet, asteroid, planetoid, natural satellite or any other astronomical body that was or could be inhabited by life forms.
The term didn't always mean that it had to be inhabited or capable of being inhabited, but in most circumstances it did. The term could also be used to describe any type of
life or anything else that inhabited the planet, asteroid or whatever it was.
From the perspective of most
humans, especially prior to interstellar space travel, the world usually referred to the Earth itself, which was also referred to as the homeworld.
Homeworld was a word that usually...although not always; referred to any life forms' world of origin. For example, Earth was the homeworld of all Earthlings, Rann was the homeworld of Rannians, Thanagar was the homeworld of Thanagarians, and Tyron VII was the homeworld of the Tyronians.
In the case of the
Psions however, their homeworld was technically Maltus, but they used the term homeworld to describe the " Psion Homeworld", which was actually a colony world.
Fourth World was a dimension or closed galaxy that contained the planets of Apokolips and New Genesis.