suggestion has 8 distinct synonyms spread across 4 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.
an idea that is suggested
“the picnic was her suggestion”
a just detectable amount
“he speaks French with a trace of an accent”
the sequential mental process in which one thought leads to another by association
Synonyms, antonyms and the broader and narrower relations for suggestion come from Princeton University’s WordNet. Full sources and licences.