WordNet records no synonym and no antonym for nature. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
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.
the essential qualities or characteristics by which something is recognized
“it is the nature of fire to burn”
a causal agent creating and controlling things in the universe
“the laws of nature”
Synonyms, antonyms and the broader and narrower relations for nature come from Princeton University’s WordNet. Full sources and licences.
the natural physical world including plants and animals and landscapes etc.
“they tried to preserve nature as they found it”
the complex of emotional and intellectual attributes that determine a person's characteristic actions and reactions
“it is his nature to help others”
a particular type of thing
“problems of this type are very difficult to solve”