What Is a ‘Quid pro Quo’?

We have the origin of "quid pro quo," and perhaps more interesting, how to make it plural.

Mignon Fogarty
5-minute read
The Quick And Dirty

The plural of "quid pro quo" can be either “quid pro quos” or “quids pro quo.” My preference is “quid pro quos.”

If you’ve been following American politics for the last few months, you are practically drowning in the phrase “quid pro quo,” and lots of people have been asking me about what it means and how to use it.

A Google trends chart that shows people have been searching for quid pro quo lately

Google Trends search results for "quid pro quo" in October 2019.

What Is a ‘Quid pro Quo’?

“Quid” and “quo” are both Latin pronouns, and the word “pro” in the middle of “quid pro quo” means “for.” Latin dictionaries and old schoolbooks give multiple meanings for these pronouns, but modern sources agree that the interpretation of the Latin phrase “quid pro quo” is “something for something.” Technically, it can mean any kind of exchange or transaction, but these days it usually has a sense of corruption, as in “Was there a quid pro quo? Did Squiggly give you those chocolate donuts for an A on that test?”

It’s generally a noun (as in “Was there a quid pro quo?”), but you can also use it as an attributive to modify a noun, as in “It’s a quid pro quo issue.”

What Is the Origin of ‘Quid pro Quo’?

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Interestingly, the phrase was used in a much more limited way when it first arose in the 16th century. According to Merriam-Webster, it was used when an apothecary substituted one kind of medicine for another, sometimes by accident and sometimes fraudulently on purpose. Sometimes it was fine—close enough—but as Ben Zimmer pointed out in an NPR interview, sometimes it would make people sick, so it wasn’t viewed as a good thing even back then. And then within just a few decades, the phrase started being used more generally.

Why Are There Two Different Latin Words for ‘Something’?

You might be wondering why we have two different words for “something”? Why isn’t it “quid pro quid” or “quo pro quo”?

Well, they aren’t two different words, exactly. According to the OED, “quō” is the ablative singular case of “quid.” Latin has more grammatical cases than English does, and the “ablative” is one of the ones we don’t have. I’m going to keep this as simple as I can. In Latin, the ablative case is often used after prepositions (like after the “pro,” which means “for,” in “quid pro quo”). 

'Quid' and 'quo' are two different forms of one Latin pronoun.

English does have the subjective and objective case for pronouns, and we use the objective case after prepositions, so you can think of the ablative as being kind of like that. “I” is the subject pronoun, and “me” is the corresponding object pronoun we’d use after a preposition in a sentence like “That’s for me.” So “quid” and “quo” are just two forms of the same pronoun in Latin, kind of the way “I” and “me” are two forms of the same pronoun in English.

How to Make ‘Quid pro Quo’ Plural

There’s been so much going on that people are starting to talk about multiple quid pro quos. Or is the plural “quids pro quo”? Or maybe even “quids pro quos”?

First, let’s stipulate that we’re not going to use the Latin plural, “quae pro quibus.” That seems ridiculous, and hardly anyone would know what you mean. It’s typical to make foreign plurals the English way once they firmly enter our language. It’s why we say our teams play in different stadiums around the country instead of different stadia, which would be the Latin plural of “stadium.”

I first checked the AP Stylebook, Chicago Manual of Style, and Merriam-Webster, but none of them addressed how to form the plural. Next, I checked the online Buzzfeed style guide because it often has guidance on words other style guides don’t (like if you hate-watch a TV show, “hate-watch” takes a hyphen), but it also failed me on the plural of “quid pro quo.” 

As an aside, the main site did, however, have a quiz “Are You a Quid, Pro, or Quo?” And the result gives you a link to a real news story about the American political situation. Well played, Buzzfeed.

Buzzfeed quiz results with a link to a news article about political quid pro quos

But then I found some sources. Both the Oxford English Dictionary and dictionary.com give two options: “quid pro quos” and “quids pro quo.” I prefer “quid pro quos” because the whole phrase is a noun—I think of it as a unit—so it makes sense to put the plural on the end. That form is also the first of the options listed at both dictionaries, and Garner’s Modern English Usage says it’s the only correct form.

'Quid pro quos' is the best plural.

You might be wondering why it’s different from the plural of “attorney general,” which is “attorneys general.” In that case, “general” is a modifier of the main noun, “attorney,” but there aren’t any modifiers in “quid pro quo.”

Can ‘Quid,’ ‘Quo,’ or ‘Quid pro Quo’ Be a Verb?

On the more obscure side, I received a question from a listener named Marcelo in Brazil who was confused by the phrase “to quid for quo.” And I saw a similar instance of “quo” being used as a verb at the end of a Columbia Journalism Review article by Merrill Perlman in the line “be careful of what you ‘quo’ for.” But these writers are just making jokes. Neither “quid” nor “quo” are typically used as verbs—remember, they’re pronouns. 

If you want to use 'quid pro quo' as a verb, write it 'quid pro quo'd.'

I also haven’t seen any authority say that the whole phrase “quid pro quo” can be a verb, although I did find multiple tweets that used it that way because whether you like it or not, we English speakers do like to verb our nouns. If you’re going to write that somebody quid pro quo’d something, use an apostrophe D at the end of “quid pro quo’d," like you would for the words “OK’d” and “ID’d.”

What Is Quiddity?

Finally, while researching this segment, I came across a delightful word that I hadn’t heard before that seems to come from the same Latin root: “quiddity.” It’s mostly used in philosophy to describe “the inherent nature or essence of a person or thing.” It’s “what makes a thing what it is,” according to the OED. Thomas Aquinas equated your quiddity with your essence.

A profile piece on the Poetry Foundation website says Ted Hughes, famous poet and Sylvia Plath’s husband, once confessed to London “Times” “that he began writing poems in adolescence, when it dawned upon him that his earlier passion for hunting animals in his native Yorkshire ended either in the possession of a dead animal, or at best a trapped one. He wanted to capture not just live animals, but the aliveness of animals in their natural state: their wildness, their quiddity, the fox-ness of the fox and the crow-ness of the crow.”

So if you get tired of hearing about quid pro quos, maybe you can ponder the quiddity of everyone involved.

Image courtesy of Shutterstock.

Mignon Fogarty is Grammar Girl and the founder of Quick and Dirty Tips. Check out her New York Times bestseller, "Grammar Girl’s Quick and Dirty Tips for Better Writing."

About the Author

Mignon Fogarty

Mignon Fogarty is the founder of Quick and Dirty Tips and the author of seven books on language, including the New York Times bestseller "Grammar Girl's Quick and Dirty Tips for Better Writing." She is an inductee in the Podcasting Hall of Fame, and the show is a five-time winner of Best Education Podcast in the Podcast Awards. She has appeared as a guest expert on the Oprah Winfrey Show and the Today Show. Her popular LinkedIn Learning courses help people write better to communicate better.