THESAURUS
side effect
accession, accessory, accompaniment, addenda, addendum, additament, addition, additive, additory, additum, adjunct, adjuvant, afterbirth, afterclap, aftercrop, aftereffect, afterglow, aftergrowth, afterimage, aftermath, afterpain, aftertaste, annex, annexation, appanage, appendage, appendant, appurtenance, appurtenant, attachment, augment, augmentation, by-product, coda, complement, concomitant, continuation, corollary, effect, extension, extrapolation, fixture, increase, increment, offshoot, pendant, placenta, reaction, reinforcement, response, secundines, side issue, supplement, tailpiece, undergirding