wonder has 7 distinct synonyms spread across 6 of its 6 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.
the feeling aroused by something strange and surprising
a state in which you want to learn more about something
place in doubt or express doubtful speculation
“I wonder whether this was the right thing to do”
Synonyms, antonyms and the broader and narrower relations for wonder come from Princeton University’s WordNet. Full sources and licences.