Irregular plural nouns | foreign plurals | The parts of speech | Grammar | Khan Academy

Hello Garans. Today we're talking about another kind of irregular plural noun, and that is the foreign plural. Those are words that are borrowed into English from some other language, words like fungus, or cactus, or thesis, or criteria. These words come from Latin and Greek respectively.

But don't get the idea that you need to learn to be able to speak Latin or Greek in order to speak English. No, not at all. While some words that got borrowed into English have lost their language-specific plurals, some have not. Some have maintained those plurals, and it kind of depends on which situation you're using them in.

For example, in an informal context, it would be perfectly acceptable for you or me to say funguses like that. But if I was talking to a biologist, she would probably say fungi if she were talking about them in a scientific context. Just like it's okay in formal speech to talk about cactuses. You're driving along the road in Arizona; you see a lot of cactuses. But again, if you studied cactuses for a living, you would probably call them cacti. It's more precise, it's more formal, if you like; it's more polite.

Now, my feeling is that as fungus and cactus get more and more entrenched into English, eventually these formal endings are going to fall away, and we're just going to have this regular plural. But for now, there are still some pluralizing rules for other languages that it helps to know. So let's go through those.

I made this little chart to go over the six most common Latin and Greek irregular plurals that you're going to encounter in English. The first one is final A to final AE. So you take a word like larvae in the singular, which is like a little baby bug like an ant larvae or a caterpillar larvae, and the traditional irregular plural, the Latin plural of that is larvea AE. But the regular plural that will probably get more popular over time is larvas.

So this is the first one: A to AE, larvae to larae, just like antenna becomes antenna. Secondly, the ending changes from final US to final I, which we find in a word like fungus as the singular, and then the irregular plural of that is fungi. As I said before, there are some people who use funguses, but again that regular plural is more informal.

This next one is also Latin, and it's the change from final to final A. So we take a word like datum, which is a single unit of data. So the plural of data, we change singular datum to plural data, and there is no accepted—you wouldn't say the datas. That is not an accepted regular plural. I think what's going to happen instead is that datum is going to fall away, but again it hasn't really happened yet—not in a formal context anyway.

This next one is also Latin, and it's final EX or final IX to final IES. So if you take a word like index or matrix, the plural of that is not indexes, but indices. Indexes is again the informal regular plural, but indices is the more formal irregular plural. Likewise, matrices.

This one is Greek, and it's the change from final IS to final ES, as in the word thesis in the singular becoming theses in the irregular plural. The regular plural, I do not care for because it is thesises, and I think that sounds silly. But thinking something is silly is no reason to stand a thwart the tide of linguistic change. Grumble, grumble.

This last one is also Greek, and it's the change from singular ON to plural A. So we take a word like criterion or phenomenon, and in the plural it is criteria or phenomena. As with datum, there isn't really a regular plural form for criteria. Nobody says criterion because the word criteria is so much better known anyway.

So these are six little ending rules. But like I said, you don't need to learn Latin or Greek in order to make sense of English. However, having these six rules in your tool belt, if you use them judiciously, will probably come in handy. But for real, if you see a word and you don't know its derivation, just trust your instincts and give it a regular plural. Just tack on an S, you know? The world's not going to end; no harm will come to you. And if you're curious, you can look it up later. You can learn anything.

Daveid out.