rule has 19 distinct synonyms spread across 14 of its 19 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.
a principle or condition that customarily governs behavior
“it was his rule to take a walk before breakfast”
something regarded as a normative example
“the convention of not naming the main character”
prescribed guide for conduct or action
(linguistics) a rule describing (or prescribing) a linguistic practice
dominance or power through legal authority
“France held undisputed dominion over vast areas of Africa”
directions that define the way a game or sport is to be conducted
“he knew the rules of chess”
any one of a systematic body of regulations defining the way of life of members of a religious order
“the rule of St. Dominic”
a rule or law concerning a natural phenomenon or the function of a complex system
“the principle of the conservation of mass”
measuring stick consisting of a strip of wood or metal or plastic with a straight edge that is used for drawing straight lines and measuring lengths
be larger in number, quantity, power, status or importance
“Money reigns supreme here”
have an affinity with; of signs of the zodiac
mark or draw with a ruler
“rule the margins”
Synonyms, antonyms and the broader and narrower relations for rule come from Princeton University’s WordNet. Full sources and licences.