furtherance has 3 distinct synonyms spread across 2 of its 2 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.
encouragement of the progress or growth or acceptance of something
the advancement of some enterprise
“his experience in marketing resulted in the forwarding of his career”
Synonyms, antonyms and the broader and narrower relations for furtherance come from Princeton University’s WordNet. Full sources and licences.