Several weeks ago, the satirical viral content site Clickhole posted this article: “Going Rogue: ‘The New Yorker’ Has Announced That They’re Going To Start Putting An Umlaut Over Every Letter ‘O’ And No One Can Stop Them”. I’ve long enjoyed poking at the New Yorker for its distractingly idiosyncratic style,* but I had a couple of quibbles with the article, so I took to Twitter to explain the history of those little dots.

First off, those little dots that appear in words like coöperation aren’t umlauts: they’re diaereses. But a few paragraphs into the article, they actually correct the headline with this fake quote from New Yorker editor David Remnick: “We already know some of you don’t like the dots. You probably call them umlauts. Well, you’re wrong: They’re actually called diaeresis, so try thinking twice before trying to correct us on how we use them.” But this just introduced another problem: diaeresis is the singular form. The plural form is diaereses. That is, the second o in coöperate has a diaeresis over it, but you’d say that the New Yorker uses diaereses in words with doubled vowels.

A diaeresis is a pair of dots that appear over a vowel to indicate that the vowel is pronounced separately from an adjacent vowel. For example, in English oo is generally pronounced as a single vowel sound, usually either the /u/ sound in boot or the /ʊ/ in book. The New Yorker puts a diaeresis over the repeated vowel in words like cooperate to show that those two o’s are pronounced as two distinct vowels. This also applies to other words with repeated vowels like reelect.

English doesn’t use very many diacritical marks, and the ones that it does use are almost entirely from foreign borrowings. But the diaeresis is uncommon in English even compared to other diacriticals. It mostly appears in French borrowings like naïveté (though naïve is often simplified to naive), where it serves the same purpose: showing that the two adjacent vowels are pronounced separately and not as a diphthong or a single long vowel. (In French, for example, ai is pronounced with the /ɛ/ sound in bet, so without the diaeresis, naive would be pronounced like Neve Campbell’s first name.)

The diaeresis goes all the way back to Ancient Greek, where it was also used the same way. Its first use, though, was to separate a vowel at the start of a new word from a vowel at the end of a preceding word, because Greek was originally written without any spaces between words. The word diaeresis comes from the Ancient Greek word for ‘division’, from diairein ‘to divide, separate’, from dia– ‘apart’ + hairein ‘take’. That is, it was simply a mark that divided two words or two adjacent vowels. Some later European languages saw the utility of a mark that indicated that two vowels were meant to be pronounced individually, and they adopted it.

But it has never been common in English outside of the pages of the New Yorker. In Confessions of a Comma Queen, former New Yorker copy editor Mary Norris briefly recounts the rationale behind the magazine’s style choice (excerpted here on Merriam-Webster’s website):

Basically, we have three options for these kinds of words: “cooperate,” “co-operate,” and “coöperate.” Back when the magazine was just developing its style, someone decided that the first could be misread and the second was ridiculous, and so adopted the third as the most elegant solution with the broadest application.

Norris also says that the style editor was on the verge of changing his mind on the diaereses back in 1978, but then he died, and “no one has had the nerve to raise the subject since.” Norris herself admits that “most people would not trip over the ‘coop’ in ‘cooperate’ or the ‘reel’ in ‘reelect'” and that diaereses are number one complaint from readers, but apparently they’re not going anywhere anytime soon. (I think that if you’re afraid to talk about changing your style guide—especially when readers find your style distracting and annoying—then you have either a bad style guide or a bad culture surrounding your style guide or both.)

But on to umlauts. Umlauts look just like diaereses—you could call diaereses and umlauts homoglyphic—but they’re used in a very different way and have a distinct origin. The umlaut symbol originated in German but has been borrowed into other languages, including Swedish, Hungarian, Turkish, and Finnish. But to understand what an umlaut does, you need to understand a little bit about where vowels are produced in the mouth.

The vowel /u/ (the sound in “boot”) is a high back vowel: it’s pronounced with the tongue pulled back and the mouth only slightly open so that the tongue is close to the roof of the mouth. The vowel /i/ (the sound in “beet”), on the other hand, is a high front vowel: it’s similarly pronounced with the mouth only slightly open so that the tongue is close to the roof of the mouth, but the tongue is pushed forward instead. If you alternate between saying “oo” and “ee”, you should be able to feel the difference. The vowel /i/ is pronounced a little behind your top front teeth, while /u/ is pronounced towards the soft palate, also known as the velum. (The vowel /u/ is also pronounced with the lips rounded, which has the effect of enhancing the distinction between it and /i/.) And the vowel /a/ (roughly like “ah”, though not every dialect of English has that exact vowel sound) is pronounced with the tongue in the middle or towards the front of the mouth and with the mouth wide open. The International Phonetic Alphabet considers it a low front vowel, but it’s also sometimes treated as a low central vowel.

What an umlaut symbol does, then, is indicate that a vowel is produced further forward in the mouth (and sometimes also higher in the mouth) than normal. For example, ü is pronounced in the same place as /i/, but it retains the lip rounding of /u/. Try saying /i/ or /ɪ/ (“ee” or “ih”) with your lips rounded, and voilà: you just made the sound of the German ü. An ö, by contrast, is like an /e/ or an /ɛ/ (roughly an “ay” or an “eh”) with lips rounded, while an ä is raised to an /e/ or an /ɛ/. (The vowel /a/ doesn’t have any lip rounding, so neither does the umlauted version.)

The term umlaut, which comes from a German word roughly meaning ‘sound change’, is also used in Germanic linguistics to refer to certain kinds of vowel changes, especially when a vowel moves closer to /i/. Sometimes, when a back or central vowel is followed by a front vowel, we start moving our tongue forward a little early in anticipation of that front vowel. In other words, the frontness of one vowel can spread backwards through the word to the preceding vowel.

English doesn’t use the umlaut mark, but it’s full of words that were produced by the phonological process of umlaut. Plurals like men, geese, feet, and mice were formed by umlaut. In Proto-Germanic, an ancestor of English that was spoken between about 500 BC and the first few centuries AD, the singular form of the word for ‘man’ was mann, and the plural was manniz. That /i/ vowel in the suffix eventually pulled the /a/ up and forward to /ɛ/, yielding the word men in English. At some point the suffix dropped away entirely, leaving only the changed vowel in the stem as evidence that it was there. In the case of geese, feet, and mice, the umlauted vowels also lost their rounding after they moved forward.

Umlaut also shows up in English in some less expected places. Have you ever wondered why words like busy and bury aren’t spelled like they’re pronounced? It’s because those words evolved in different ways in different Old English dialects. In some dialects, the first vowel umlauted and then lost its rounding, ultimately yielding an /ɪ/ or an /ɛ/. But in other dialects, they didn’t undergo umlaut, retaining the original /u/. At some point the two forms mashed up, and we got the spelling of one dialect and the pronunciation of another. The weird alternations in words like bring/brought and teach/taught are also the product of umlaut, with a couple other phonological changes thrown in for good measure.

So if the phonological process of umlaut is common to English, German, and other Germanic languages, why does German use the umlaut character but not English? It’s simply because the writing systems of each language developed separately after many of those sound changes had happened. For example, the modern German word schön was written schoene in Middle High German (around 1050 to 1350 AD). That final -e on the end, which has since dropped off, caused the o to become umlauted. But then, to make it clear that the o was pronounced with an umlaut, people started writing another e after the o too. Then they started writing that e above the o rather than after it to show that it was affecting the vowel but wasn’t really pronounced, and eventually this superscript e simplified to two short vertical strokes or two dots.† And thus the confusion between diaereses and umlauts was born.

So there you have it: The diaeresis is originally a Greek thing that indicates that two adjacent vowels are pronounced separately. In English, you’ll mostly see it in a few French borrowings or in the pages of the New Yorker. And the umlaut is originally a German thing, though it also represents a phonological process found in English and other languages. There aren’t a lot of German borrowings in English that use umlauts, so you mostly see it in the names of bands that are trying to look a little more metal.

Nöw yöu knöw.

* The New Yorker’s style inspired one of my favorite style-related tweets, from the inimitable Benjamin Dreyer:

One's house style oughtn't to be visible from outer space. #totallynotasubtweet

— Benjamin Dreyer (@BCDreyer) April 10, 2018

† The tilde and cedilla were formed in similar ways. A tilde was originally just a superscript n, while a cedilla was a subscript z. The history of the latter is even right there in its name: a cedilla is a little ceda, an Old Spanish form of zeta.