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What’s the Plural of Addendum?

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What’s the plural of “addendum”?

The plural of an addendum is addenda and addendums. An addendum, which is “something that has been added to a book, speech, or document”, is synonymous with appendix or supplementary material. Typically, addenda will include notes or material missing from the main text or work.

👍🏼Usage Note

The report included several important addenda at the end.

Please read through the new addendums before the meeting.

The contract has three addendum that need approval.

They added a few more addendum to the original document.

Addendum has two plural noun forms: both addenda and addendums are correct, though the former is the original Latinate pl. n. form.  Addendums, on the other hand, uses the standard pl. n. modifier in English by adding the –s at the end to show a plural. This standard form most likely came to be adopted as a plural for addendum over time, and through the consistent mistaking of addendums as the plural form.

Irregular plural nouns that end in um-/-a

Though unusual, addendum is by no means the only Latin noun that has sustained until Modern English. See the chart of irregular nouns that end in -um as a singular noun, and convert to -a as a plural:

singular plural
colloquium colloquia or colloquiums
referendum referenda or referendums
memorandum memoranda or memorandums
curriculum curricula or curriculums
addendum addenda or addendums
symposium symposia or symposiums

Addendum in context (in sentences)

1. Alex added some personal remarks in the addendum of his letter.

2 .Maria’s article was written in 1965, but it was updated with an addendum in recent years.

3. I added an addendum to the report in which I highlighted certain legal issues that our company was facing.

4. It would be smart to add an addendum to your resume to highlight some of your areas of expertise.

5. If you read the addendum to Oliver’s biography, you will learn about the lesser known aspects of his life.

💡Study Tip

To make “addendum” plural, remember you *add* -a or -s: addenda or addendums.

Addenda/addendums in context (in sentences)

1. “We want to address the new addenda of the CMO,” said Glen Hartman, head of Accenture Interactive North America.

2. Make sure the lease contains signatures by both parties and all amendments, addenda, renewals, etc., are located and included. –OC Register

3. The lawyers introduced various addenda to the contract.

4. This includes the table of contents and any attachments or addenda .

5. They are extraneous addenda , and insidious ones at that.

Addendum synonyms

Origin of the word addendum

From etymonline on addendum, from Latin addendum, neuter of addendus “that which is to be added”.

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Work Sheet

Question 1 of 10

According to the blog post, what is the primary meaning of “addendum”?



Which of the following is considered a correct plural form of “addendum” by the blog post?



The blog post mentions that “addenda” is the original plural form. Where does this form come from?



According to the post, what is a common mistake people make when trying to use the plural of “addendum”?



Which pair of words from the post follows a similar -um/-a plural pattern to “addendum/addenda”?



The report included several important at the end.



Please read through the new before the meeting.



The contract has three that need approval.



Maria’s article was written in 1965, but it was updated with an in recent years.



Make sure the lease contains signatures by both parties and all amendments, , renewals, etc., are located and included.





Frequently Asked Questions

What are the plural forms of addendum?
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The post states that both addenda and addendums are considered correct plural forms. Addenda is the traditional Latinate form, while addendums uses the standard English ‘-s’ ending.

Which addendum plural is traditional?
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The traditional and original Latinate plural form of addendum is addenda. The post mentions it is considered the ‘correct traditional plural form’ in usage notes provided.

Why does addendum have two plurals?
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Addendum is a Latin noun. Its original Latin plural is addenda (-um to -a). The form addendums developed later by adding the standard English ‘-s’ plural ending.

What’s a common mistake using addendum?
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A common mistake highlighted in the post is using the singular form ‘addendum’ as a plural, as shown in examples like “The contract has three addendum that need approval.”

Example usage for addendum plurals?
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For the traditional form: “The report included several important addenda at the end.” For the modern form: “Please read through the new addendums before the meeting.”

Yash, D. "What’s the Plural of Addendum?." Grammarflex, Jun 5, 2025, https://www.grammarflex.com/whats-the-plural-of-addendum/.

Sources

  1. Synonyms of addendum.

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