Synonyms for addition

noun

1. The process of adding

   reckoning, computing, totaling, summing up, summation, enlarging, accruing, increasing, expanding, tabulating, counting, accretion, joining, uniting, appending, annexing.

   Antonyms subtraction, reduction*, lessening.

2. That which has been added

   interest, raise, additive, adjunct, augmentation, addendum, profit, profits, dividend, dividends, bonus, commission, increment, supplement, gain, insert, accretion, accession, accrual, subordinate part, enhancement, aggrandizement, reinforcement, appendage, appendix, accessory, appurtenance, attachment, extension, increase, annex, affix, appreciation.

   Antonyms loss*, reduction*, shrinkage.

3. An architectural extension

   wing, ell, annex, spare room, extension; see also room 2.