remainder has 9 distinct synonyms spread across 3 of its 5 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 part of the dividend that is left over when the dividend is not evenly divisible by the divisor
the number that remains after subtraction; the number that when added to the subtrahend gives the minuend
a piece of cloth that is left over after the rest has been used or sold
sell cheaply as remainders
“The publisher remaindered the books”
Synonyms, antonyms and the broader and narrower relations for remainder come from Princeton University’s WordNet. Full sources and licences.