economy has 3 distinct synonyms spread across 3 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.
the system of production and distribution and consumption
the efficient use of resources
“economy of effort”
frugality in the expenditure of money or resources
“the Scots are famous for their economy”
an act of economizing; reduction in cost
“it was a small economy to walk to work every day”
Synonyms, antonyms and the broader and narrower relations for economy come from Princeton University’s WordNet. Full sources and licences.