chance has 17 distinct synonyms spread across 7 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.
a possibility due to a favorable combination of circumstances
“the holiday gave us the opportunity to visit Washington”
a risk involving danger
“you take a chance when you let her drive”
a measure of how likely it is that some event will occur; a number expressing the ratio of favorable cases to the whole number of cases possible
“the probability that an unbiased coin will fall with the head up is 0.5”
take a risk in the hope of a favorable outcome
“When you buy these stocks you are gambling”
Synonyms, antonyms and the broader and narrower relations for chance come from Princeton University’s WordNet. Full sources and licences.