addendum (n.)

• accession
• accessory
• accident
• accidental
• accompaniment
• addition
• additive
• adjunct
• adjuvant
• afterthought
• annex
• annexation
• appanage
• appendage
• appendix
• appurtenance
• attachment
• augmentation
• auxiliary
• chorus
• coda
• codicil
• collateral
• colophon
• complement
• conclusion
• concomitant
• consequence
• contingency
• contingent
• continuance
• continuation
• corollary
• envoi
• epilogue
• extension
• extra
• extrapolation
• fixture
• follow-through
• follow-up
• happenstance
• incidental
• increase
• increment
• inessential
• nonessential
• offshoot
• other
• pendant
• peroration
• postfix
• postlude
• postscript
• refrain
• reinforcement
• rider
• secondary
• sequel
• sequela
• sequitur
• subscript
• subsidiary
• suffix
• supplement
• tag
• tailpiece