Redundonyms: Why It’s WRONG To Say “ATM Machine” and “PIN Number”

Is redundonym a made-up word? The spell-check feature on my computer certainly seems to think so. But it’s a perfectly good word to describe redundant acronyms, plus it’s just super fun to say out loud (it bounces down your tongue very nicely).

Redundant + Acronym = Redundonym

Acronyms are words that are formed from the initial letter (or letters) of each word in a compound word. (For the purposes of this article, I’m lumping in initialisms with acronyms. To learn more about the difference between the two, check out this article!)

When an acronym is followed by a word that is already part of the acronym itself, we can call it a redundonym.

Some examples of redundonyms include ATM machine (“ATM” stands for “automated teller machine”), GRE exam (“GRE” stands for “graduate record exam”), and PIN number (“PIN” stands for “personal identification number”). “Machine,” “exam,” and “number” are already part of those three acronyms (respectively), so there’s no reason to say or write the words twice.

Another popular name for these terms is RAS syndrome, which is in itself a redundonym because “RAS” stands for “redundant acronym syndrome.”

As a general rule, it’s best to avoid redundancies, especially in writing. That’s why redundonyms are usually frowned upon.

Examples

Here are more examples of common redundonyms:

• SSN Number (“SSN” stands for “social security number”)
• ISBN Number (“ISBN” stands for “international standard book number”)
• UPC Code (“UPC” stands for “universal product code”)
• APO Office (“APO” stands for “Army Post Office”)
• MLB Baseball (“MLB” stands for “Major League Baseball”)
• HIV virus (“HIV” stand for “human immunodeficiency virus”)
• UPS service (“UPS” stand for “United Parcel Service”)
• DSW shoes (“DSW” stands for “Designer Shoe Warehouse”)
• LCD display (“LCD” stands for “liquid-crystal display”)
• DC Comics (“DC” stands for “Detective Comics”)
• Please RSVP (RSVP stands for répondez s’il vous plaît. Translating that into English, this becomes “Please respond if you please.”)

Why Are Redundonyms Bad?

Ebbitt & Ebbitt said it best in the Index to English: “In writing, words and phrases that are repetitive or simply unnecessary are redundant.” Redundancy is a thing to be avoided at all costs, as it tends to create unnecessary wordiness.

Wherever possible, writers try to simplify and condense their writing to promote clarity and prevent confusion.

Redundonyms are unfortunately very common in spoken English, but they’re considered poor form in written English (especially in formal writing).

Most style guides suggest writers avoid redundonyms, but that’s not the only reason to keep them out of your writing. Using a redundonym might make you look silly: If you write “PIN number,” it sounds like you don’t actually know what “PIN” stands for.

When Should You Put Up With Redundonyms?

Is there ever a reason to allow a redundonym to slip into your writing? …Maybe. There are a few instances where using a redundonym may be helpful, but most of the time you’re better off just spelling out the acronym.

You might use a redundonym when an acronym is not well-known, but again, it’s usually better to simply spell it out.

Redundonym: Be sure to memorize your SSN number.

Correct: Be sure to memorize your SSN.

Also correct and helpful if the audience may not know what SSN stands for: Be sure to memorize your social security number.

Redundonyms are also common when an acronym is in a language that the audience may not speak. In this situation, I think redundonyms are more forgivable because spelling out and then translating the acronym may look clunky and awkward.

Redundonym: Please RSVP to the party ASAP.

Technically correct: RSVP to the party ASAP.

The problem with this “correct” version is that it changes the tone: Without the “please,” it may come off as more blunt than the writer intends.

Also technically correct but awkward: RSVP (“répondez s’il vous plaît,” meaning “respond if you please) to the party ASAP.

In this situation, the redundonym is the best choice.

There’s also something called an obsolete redondonym, where an acronym used to stand for something but doesn’t anymore. One example of this is the SAT test. SAT used to stand for “scholastic aptitude test,” and then it was changed to “scholastic assessment test.” With these acronyms, “SAT test” was a redundonym (scholastic assessment test test). However, in 1997, the College Board announced that “SAT is not an initialism. . . . The SAT has become the trademark; it doesn’t stand for anything.” Because SAT no longer stands for anything, it’s no longer incorrect to call it the SAT test.

What do you think about redundonyms? Do you consider them to be necessary or problematic? Let me know in the comments!

Should you use “a” or “an” before an acronym? Learn the EASY rule here!

Sources:

• Ebbitt, D. R., and W. R. Ebbitt. Index to English. 8th ed. New York: Oxford University Press, 1990.
• Einsohn, Amy. The Copyeditor’s Handbook. 3rd ed. Berkeley and Los Angeles, California: Univ of California Pr, 2011.
• “RAS Syndrome.” Wikipedia, January 7, 2025. https://en.wikipedia.org/wiki/RAS_syndrome.