Plural of Addendum
“Addendum” has two current dictionary-recorded plurals: “addenda” and “addendums.” Cambridge foregrounds “addenda,” while Merriam-Webster also records “addendums,” so a writer can use either accepted form unless a house style requires one.
Both “addenda” and “addendums” are accepted plurals of “addendum.”
Key details
Choose the right form
| Meaning / situation | Form / construction | Decision |
|---|---|---|
| one addition | addendum | Singular. |
| more than one | addenda | Accepted plural. |
| more than one | addendums | Also accepted plural. |
Quick tests
Plural-choice test
Are you referring to more than one addendum?
If yes: Use “addenda” or “addendums.”
If no: Use singular “addendum.”
Caveat: A publication may impose a house preference, but the reviewed dictionary evidence supports both plural forms.
Examples
The contract contains two addenda.
“Addenda” is an accepted plural.
The report has several addendums.
“Addendums” is also recorded as a plural.
An addendum explains the revised deadline.
One addition takes singular “addendum.”
Further guidance
Core difference
Use “addenda” or “addendums” for more than one addendum.
Fast Test
If a document already uses one plural form, keep that form consistent; otherwise either accepted plural is available.
Usage Boundary
Do not mark “addendums” wrong merely because “addenda” is the traditional Latin-derived plural.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- ADDENDUM Definition & Meaning - Merriam-Webster (opens in a new tab)Merriam-Webster · Merriam-Webster records plural addenda and also addendums.
- ADDENDUM | English meaning - Cambridge Dictionary (opens in a new tab)Cambridge University Press · Cambridge records addenda as the plural of addendum in publishing and business treatment.