erosion has 6 distinct synonyms spread across 2 of its 4 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.
(geology) the mechanical process of wearing or grinding something down (as by particles washing over it)
condition in which the earth's surface is worn away by the action of water and wind
a gradual decline of something
“after the accounting scandal there was an erosion of confidence in the auditors”
erosion by chemical action
Synonyms, antonyms and the broader and narrower relations for erosion come from Princeton University’s WordNet. Full sources and licences.