world has 25 distinct synonyms spread across 8 of its 9 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
everything that exists anywhere
“they study the evolution of the universe”
people in general; especially a distinctive group of people with some shared interest
“the Western world”
all of your experiences that determine how things appear to you
“his world was shattered”
the 3rd planet from the sun; the planet we live on
“the Earth moves around the sun”
a part of the earth that can be considered separately
“the outdoor world”
the concerns of this life as distinguished from heaven and the afterlife
“they consider the church to be independent of the world”
all of the living human inhabitants of the earth
“all the world loves a lover”
involving the entire earth; not limited or provincial in scope
“global war”
Synonyms, antonyms and the broader and narrower relations for world come from Princeton University’s WordNet. Full sources and licences.