BONUS VIDEO | Origin of the Mutant Plural | Grammar | Khan Academy

Hello grammarians! I wanted to talk to you again about mutant plurals. So, to review, a mutant plural is... there are only seven of them in English, and they all change sound when they pluralize. You don't add an "s," you don't add an "en," you don't change the ending; you change the vowel. And there's only seven. They go like this: there's man, woman, tooth, foot, mouse, louse, and goose.

And these words become, in the plural: men, women, teeth, feet, mice, lice, and geese. Now, the reason that we have these seven weird mutant plurals in English is kind of complicated, but I'm lucky enough to be able to work with an actual linguist.

Hello, Jake.

Hey grammarians! Jake, is it true that you are a linguist?

Yup, it's true.

All right, so Jake, what is the deal with feet? Where do these mutant plurals come from?

If we take the word "foot" and we drag it through history, how do we get to the plural as "feet"? What's the deal with that?

So, if you look at a lot of Germanic languages that are around today, you find similar words to the English word "foot." In German, we have the word "Fuss," in Dutch we have the word "voet." And when you have a lot of different languages with slight variations of a word, it means there's some old, old word out there that all these words are coming from.

So we can pretty much be sure that there's some Proto-Germanic word that sounds something like "foot." Now, back in those days, there was a different way to form the plural, and that was to add an "e" sound at the end of a word. So, if the word was "fut," then the plural was maybe "futi" - that means "many foots."

Now, there's a tendency in language that you have to understand here: it's called vowel harmony. It basically means that vowels within a given word like to sound like each other. So if you have two syllables, those syllables will start to con... the vowels in those syllables will start to converge.

Um, and in Germanic languages especially, there's one typical kind of vowel harmony, which is okay that you have two vowels in a word; the first vowel will try to sound more like the second vowel if that second vowel is the "e" sound, just like in the plural formation of nouns.

So you're saying that the suffix "e" at the end of this proposed word "futi," the "u" sound tried to sound more like the "e" sound?

This is just a pattern that we found in Germanic languages.

Exactly, it's very prevalent in Germanic languages. It also exists in some Romance languages, some tiny Romance languages.

So, what happens when you combine the "oo" sound with the "e" sound? What sound do you get?

Well, strangely, you get the "ee" sound.

What is that? Are you okay?

I think I'm okay. You know, we linguists have to deal with this kind of thing all the time. We have very strong stomachs.

You still get this sound in languages like German and Dutch.

So then, that's what this "e" is, right?

So, this sound, or I guess the plural of German "foos," is what you said.

So, okay, bring this home for me. At some point in the development of English or of all these Germanic languages, we had the word "foot," and then it turned into "futi," and then it turned into what?

And turned into "fuji," something like "futi."

Right. Okay, now eventually that "e" sound dropped out of English, which is why it's so hard for us to pronounce, and it was replaced in pretty much all cases with the "e" sound. So we get the word "fiti," and then the "e" drops off, and we're left with "foot" as the singular and "feet" as the plural.

Cool, so it goes from "foot" to "fiti."

Now, the same exact thing happened with the word "mouse," which probably used to be "moose," because in Frisian, which is the closest cousin to English, the word for "mouse" still is "moose." You find similar things in a lot of Germanic languages, like "muis" in Dutch and "Maus" in German.

The plural became "musi," and then eventually "mesi." Then you get "meis," and during a few hundred years later, during the Great Vowel Shift, that "meese" becomes "mice." A lot of "e" vowels in the Great Vowel Shift, about 500 years ago, became "i" vowels.

So, this is sort of the broad pattern these mutant words all take: this umlaut mutation, right?

Because this little... these double dots that go over a vowel change its color, right? Change its meaning?

And that process is called either umlaut mutation or "i" mutation. Not "I" like the sight organ; I like the letter in English.

Cool! Well, I hope that cleared some things up for you.

You can learn anything.

David out.

Jake out.

That was a high five, not a slap!