5
annexe(noun, adjunct)
5
insert(noun, increase, extra, addition, supplement)
4
amendment(noun, act, measure, qualification, provision)
4
auxiliary(noun, addition, attachment, accompaniment)
4
cast
4
complement(noun, increase, extra, addition, attachment)
4
rider(noun, act, increase, measure, extra)
4
sequel(noun, increase, extra, addition, additive)
3
addenda
3
admixture
3
enlargement(noun, increase, delay, development, extra)
3
epilogue
3
fixture(noun, accompaniment)
3
reinforcement(noun, extra, supplement, appendage, adjunct)
3
secondary(noun, accompaniment)
3
supplementation
2
accrual(noun, extra, supplement, appendage, add-on)
2
additament
2
additive(noun, increase, extra, addition, supplement)
2
additum
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APASmart Define. (2015). addendum thesaurus. Retrieved September 21, 2026, from https://smartdefine.org/addendum/thesaurus/synonyms
ChicagoSmart Define. 2015. "addendum thesaurus" https://smartdefine.org/addendum/thesaurus/synonyms (accessed September 21, 2026).
HarvardSmart Define 2015, addendum thesaurus, Smart Define, viewed 21 September, 2026, <https://smartdefine.org/addendum/thesaurus/synonyms>.
MLASmart Define. "addendum thesaurus" 13 April 2015. Web. 21 September 2026. <https://smartdefine.org/addendum/thesaurus/synonyms>