amount has 9 distinct synonyms spread across 5 of its 7 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 relative magnitude of something with reference to a criterion
“an adequate amount of food for four people”
how much there is or how many there are of something that you can quantify
a quantity obtained by the addition of a group of numbers
be tantamount or equivalent to
“Her action amounted to a rebellion”
Synonyms, antonyms and the broader and narrower relations for amount come from Princeton University’s WordNet. Full sources and licences.