manifestation has 6 distinct synonyms spread across 3 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 clear appearance
“a manifestation of great emotion”
Synonyms, antonyms and the broader and narrower relations for manifestation come from Princeton University’s WordNet. Full sources and licences.
a manifest indication of the existence or presence or nature of some person or thing
“a manifestation of disease”
an appearance in bodily form (as of a disembodied spirit)
expression without words
“tears are an expression of grief”
a public display of group feelings (usually of a political nature)
“there were violent demonstrations against the war”