ILLUSTRATION BY ELLEN SURREY

Not long ago, I walked into a friend’s kitchen and found her opening one of those evil, impossible-to-breach plastic blister packages with a can opener. This worked, and struck me as brilliant, but I mention it only to illustrate a characteristic that I admire in our species: given almost any entity, we will find a way to use it for something other than its intended purpose. We commandeer cafeteria trays to go sledding, “The Power Broker” to prop open the door, the Internet to look at kittens. We do this with words as well—time was, spam was just Spam—but, lately, we have gone in for a particularly dramatic appropriation. In certain situations, it seems, we have started using “no” to mean “yes.”

Here’s Lena Dunham demonstrating this development, during a conversation with the comedian Marc Maron on his podcast “WTF.” The two are talking about people who reflexively disparage modern art:

MARON: They can look at any painting and go, “Eh.” They can look at a Rothko and go, “Hey, three colors.” And then you want to hit them.

DUNHAM: No, totally.

Dunham is twenty-eight years old, but the “No, totally!” phenomenon is not limited to her generation. It’s not even limited to “No, totally.” I first started noticing it when a fiftysomething acquaintance responded to a question I asked by saying, “Yup! No, very definitely.” That sent me looking for other examples, which turn out to be almost nonexistent in written English but increasingly abundant in speech. In 2001, the journalist Bernard Kalb told the White House correspondent Dana Milbank that it was the job of reporters to thoroughly investigate political candidates, to which Milbank responded, “Oh, no, yes, I agree with you there.” In 2012, Anderson Cooper, talking with the CNN senior political analyst Gloria Borger, referred to Newt Gingrich as “the guy who has come back from the dead multiple times.” Borger’s reply veered toward Molly Bloom terrain: “Yes, no, exactly, exactly, exactly.”

“No, totally.” “No, definitely.” “No, exactly.” “No, yes.” These curious uses turn “no” into a kind of contranym: a word that can function as its own opposite. Out of the million-odd words in the English language, perhaps a hundred have this property. You can seed a field, in which case you are adding seeds, or seed a grape, in which case you are subtracting them. You can be in a fix but find a fix for it. You can alight from a horse to observe a butterfly alighting on a flower.

Such words—also called auto-antonyms, antagonyms, Janus words, and antiologies—can arise for different reasons. Some are just a special kind of homonym; what appears to be one word with two opposite meanings is really two different words with identical spellings and pronunciations. Thus “clip,” meaning “to attach together,” comes from the Anglo-Saxon clyppan, while “clip,” meaning “to cut off,” comes from the Old Norse klippa. Other contranyms arise when nouns becomes verbs. Sometime around 1200 A.D., dust turned into a verb and, as dust will do, went every which way: “to dust” can mean to remove dust, as from a bookshelf, or to add something dusty, as flour to a cake pan or snow to the streets of Brooklyn. Alternatively, a contranym can reverse meanings when it is used as a different part of speech. As a noun, “custom” refers to a behavior that is common to many people. As an adjective, it refers to something designed for just one person.

Occasionally, however, a contranym arises through a process called amelioration, whereby a normally negative word develops a secondary, positive meaning. This phenomenon is particularly common in slang: “bad” becomes good, “wicked” becomes awesome, and “sick” and “ill” become wonderful. (They have been ameliorated: made better.) The use of “no” to mean “yes” appears to be an example of amelioration, but with one important distinction: “no” can’t mean “yes” on its own. Consider a slightly abridged version of Lena Dunham’s conversation about art appreciation:

MARON: And then you want to hit them.

DUNHAM: No.

Take away the “totally” and Dunham appears to be rejecting anti-philistine violence. By contrast, you can take away the “no” without doing any evident semantic damage at all. A perfectly fine response to “Then you want to hit them” is “Totally”—or, for that matter, “Yes, totally,” or just “Yes.” In fact, every instance of “No, totally” and its kindred phrases can be replaced with “Yes,” without any disruption of grammar or meaning. So why do we sometimes use “no” instead?

At first blush, “no” does not appear to be the kind of word whose meaning you can monkey with. For one thing, there is its length. At just two letters and one syllable, it lacks the pliable properties of longer words. You can’t stuff stuff inside it. (You can say “unfreakingbelievable,” but you cannot say “nfreakingo.”) You can’t mangle it, à la “misunderestimate” or (the finest example I’ve heard lately) “haphazardous.” On the contrary, it is so simple and self-contained that it is a holophrasm, a word that can serve as a complete sentence. (Holophrasms aren’t common in English, but any verb in command form can be holophrastic—“Go,” “Help,” “Run”—and babies just learning to talk use single words to express complex ideas all the time, albeit without regard to grammar: “Ball,” “Up,” “Want.”) Moreover, the word has the apparent fixity and clarity of a logical operator: like “if,” “then,” “and,” “or,” and “not,” “no” seems designed to be unambiguous. When we ask, in the face of excessive pestering, “What part of ‘no’ don’t you understand?,” what we mean is: “Unless you are a complete cretin, there is no part of ‘no’ that you could possibly misunderstand.”

Well, perhaps you would care to join me for a while in the land of complete cretinhood. For instance, answer me this, if you can: What part of speech is “no”? I thought it over for a while and concluded that it must be an interjection, even though it fails the Mad Libs test. (“The burglar bumped into the dresser and exclaimed, ‘___, my toe!’ ” The last time someone filled in a blank like that with “no” was never.) At a generous estimate, I was only one-sixth correct—but, in my defense, “no” resists all ready grammatical categorization. It is not an interjection, except when it is. (“Oh, no, I missed the train.”) It is not a noun, except when it is. (“The nos have it.”) It is not an adjective, except when it is. (“I have no idea what you’re talking about.”) It is not an adverb, except when it is. (“I’m no clearer on this than I was when I began.”) Some linguists grant it the separate part-of-speech status of “sentence word,” because, as I noted, it can serve as a stand-alone sentence. Others consider it a particle—even though, as a rule, the point of particles is precisely that they can’t stand alone; they exist to affect the meaning of other words.