determination has 4 distinct synonyms spread across 4 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.
Synonyms, antonyms and the broader and narrower relations for determination come from Princeton University’s WordNet. Full sources and licences.
the quality of being determined to do or achieve something; firmness of purpose
“his determination showed in his every movement”
a position or opinion or judgment reached after consideration
“a decision unfavorable to the opposition”
deciding or controlling something's outcome or nature
“the determination of grammatical inflections”
the act of making up your mind about something
“the burden of decision was his”