addition

1 a smaller structure added to a main building a new addition to the library providing space for an expanded video collection Synonyms annex, extension, penthouseRelated Words arm, ell, wing

2 something added (as by growth) the cache of old stamps I found in the discarded desk was a huge addition to my stamp collection Synonyms accretion, accrual, addendum, increase, augmentation, boost, expansion, gain, increment, more, plus, proliferation, raise, rise, step-up, supplement, 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

3 the act or process of becoming greater in number how do you account for the addition of more paint stains on your shirt after you put on a smock? Synonyms accumulating, accumulation, multiplication, increase, mushrooming, proliferationRelated Words doubling, quadrupling, tripling; creep, growth, rise, spread; enlargement, escalation, expansion; amplification, distension (or distention), inflation; accretion, accrual, augmentation, cumulation; extension, lengthening; boost, gain, hike, increment, riseNear Antonyms abatement, compressing, compression, condensation, condensing, constricting, constriction, contracting, contraction, diminishing, diminishment, diminution, drop, drop-off, fall, falloff, lessening, lowering, reduction, shrinkage, shrinking; retrenching, retrenchment, shorteningAntonyms decrease