Synonyms for Remainder (same or very similar meaning)
WordNet sense 1 (something left after other parts have been taken away):
balance, residual, residue, residuum, rest
WordNet sense 2 (the number that remains after subtraction; the number that when added to the subtrahend gives the minuend):
difference
WordNet sense 3 (a piece of cloth that is left over after the rest has been used or sold):
end, oddment, remnant
From the ODE community, based on WordNet
add/edit