cause has 19 distinct synonyms spread across 6 of its 7 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.
events that provide the generative force that is the origin of something
“they are trying to determine the cause of the crash”
a justification for something existing or happening
“he had no cause to complain”
a series of actions advancing a principle or tending toward a particular end
“he supported populist campaigns”
any entity that produces an effect or is responsible for events or results
a comprehensive term for any proceeding in a court of law whereby an individual seeks a legal remedy
“the family brought suit against the landlord”
Synonyms, antonyms and the broader and narrower relations for cause come from Princeton University’s WordNet. Full sources and licences.