Addendums

Addendums are documents appended to an existing document to add information, clarify terms, correct errors, or modify content. They serve as supplementary material that preserves the original document while incorporating new or revised terms. The term is used across contexts such as legal contracts, publications, and data records. In common usage, addendum and addenda are the preferred terms for the supplement; some writers use addendum plural forms like addendums, though this is less standard.

In contracts and agreements, an addendum (or addendum to the contract) modifies the original terms without rewriting the entire document. It should clearly identify the original contract, describe the changes, specify the effective date, and be signed by all parties. Addenda may address pricing, schedules, scope of work, or new obligations. In many jurisdictions, mutual assent to the addendum suffices for modification; formal consideration is not always required. Addenda are usually kept with the original contract and become part of the binding agreement.

In publishing and records, an addendum can provide post-publication notes, corrections, updates, or additional data. Scholarly works may use addenda to supply supplementary information that complements the main text without altering its narrative.

See also: amendment, appendix, erratum, supplement, addenda. Note that the broader concept of an addendum differs from the mathematical term addend, which refers to a number added in a sum.