addendum

American  

[uh-den-duhm] / əˈdɛn dəm /

noun

• addenda,
  plural
• addendums
  plural

1. a thing to be added; an addition.

2. an appendix to a book.

3. Machinery.

   1. the radial distance between the tip of a gear tooth and the pitch circle of a gear or the pitch line of a rack.

   2. Also called addendum circle. an imaginary circle touching the tips of the teeth on a gear.

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addendum British  

/ əˈdɛndəm /

noun

1. something added; an addition

2. a supplement or appendix to a book, magazine, etc

3. the radial distance between the major and pitch cylinders of an external screw thread

4. the radial distance between the pitch circle and tip of a gear tooth

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Other Word Forms

Noun Inflected Forms

• addenda
  plural
• addendums
  plural

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Etymology

Origin of addendum

First recorded in 1785–95; neuter singular of Latin addendus “that which is to be added,” gerundive of addere “to add”; see add

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Explanation

When you make an addendum to a document, you are adding text to the end. Addenda tend to be serious business as they're added to contracts, reports, and studies. There is nothing dumb about an addendum; often an addendum makes a document "smarter" by adding more information. If you did a science report on plant growth and found that after your study was complete, the plant flowered in an unusual way, you might describe that as an addendum to your report. Fun fact: the plural of addendum is addenda.

Example Sentences

See Examples For:

addendum addenda addendums

That addendum removes a requirement that the unit be owner-occupied and allows the lender to collect rent directly from tenants if Paxton were to default on the loan.

From Salon ● Sep. 5, 2026

Román would make the decision “based on” a point system that differed from what was laid out in the original request for proposals, according to an addendum sent to the bidders.

From Los Angeles Times ● Sep. 4, 2026

"The addendum does not have one of those points raised in that leaked email," he said.

From BBC ● Aug. 21, 2026

Attorneys can work specific language about dementia care into advance directives, but for many people, having a dementia directive as an addendum is a cost-effective option.

From The Wall Street Journal ● Jul. 3, 2026

“And now,” Miss Spink said, “Miriam and I proudly present a new and exciting addendum to our theatrical exposition. Do I see a volunteer?”

From "Coraline" by Neil Gaiman

In addition to the request for increased compensation, Hearn said his list of addenda covers practical matters including travel, accreditation and media arrangements.

From BBC ● Aug. 21, 2026

The retired brass and veterans organizations added emotionally charged addenda to that legalistic document.

From Los Angeles Times ● Feb. 28, 2025

Teamsters-represented UPS workers are also covered under supplemental agreements, riders and addenda that are specific to the region where they work.

From Reuters ● Apr. 12, 2023

In one of Piepenberg’s addenda, Prince also discusses musical “alphas,” giving the examples of himself, Michael Jackson, and Beyoncé, and why it’s sometimes better for artists to be less than democratic in their leadership approach.

From Slate ● Oct. 30, 2019

Naturally Father had his own addenda for the meeting.

From "The Poisonwood Bible" by Barbara Kingsolver

The eventual pact could look much different from the trilateral agreement that took effect in 2020, perhaps with separate addendums for Canada and Mexico, Shaw added.

From The Wall Street Journal ● Jul. 1, 2026

Three "addendums" remain secret and will only be shared with Ukraine's partners, Zelensky said.

From BBC ● Oct. 16, 2024

In the show’s final season, the family patriarch’s heirs struggled to decode penciled-in addendums to his last wishes that were found locked in a safe.

From New York Times ● Jul. 9, 2023

Alas, her name isn’t listed among the penciled addendums from unspecified eras.

From Salon ● Apr. 17, 2023

Note: A Drama on the Seashore is also known as A Seaside Tragedy and is referred to by that title in other addendums.

From A Drama on the Seashore by Katharine Prescott Wormeley

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Related Words

• appendix
• postscript

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