reign has 5 distinct synonyms spread across 2 of its 5 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 period during which something or somebody is dominant or powerful
“he was helpless under the reign of his egotism”
the period during which a monarch is sovereign
“during the reign of Henry VIII”
Synonyms, antonyms and the broader and narrower relations for reign come from Princeton University’s WordNet. Full sources and licences.
have sovereign power
“Henry VIII reigned for a long time”
be larger in number, quantity, power, status or importance
“Money reigns supreme here”