supplement

1 something added (as by growth) this new rule restricting e-mail to job-related activity is only a supplement to the preexisting policy regarding personal use of company resources Synonyms accretion, accrual, addendum, addition, augmentation, boost, expansion, gain, increment, more, plus, proliferation, raise, rise, step-up, increase, uptickRelated Words accumulation, assemblage, collection, gathering; complement; accession, appendix, continuation, extension, uptrend, upturn; jump, run-up, spikeNear Antonyms deduction, subtractionAntonyms abatement, decline, decrease, decrement, depletion, diminishment, diminution, drop-off, fall, falloff, lessening, loss, lowering, reduction, shrinkage, step-down

2 something that serves to complete or make up for a deficiency in something else recommends taking a vitamin C supplement to prevent colds Synonyms correlate, complementRelated Words addendum, addition, appendix; adjunct, annex, appendage, extension; accessory (also accessary), accompaniment, appliance, attachment; additive, filler

3 a part added at the end of a book or periodical a supplement containing biographical articles on women who had died since the publication of the original three-volume encyclopedia Synonyms afterword, appendix, codicil, excursus, addendumRelated Words coda, epilogue (also epilog), postlude; conclusion, ending, finale; accompaniment, addition, complement, postscript; follow-up, sequel; documentation; allonge, riderAntonyms foreword, introduction, preface, prologue (also prolog)