A Word, Please: Latin plurals can defy English standards

Algae thrives in sunlight. Or is it algae thrive?

These are the questions that can broadside a copy editor years, even decades, into her career. When it comes to English, there's never a point where you can sit back and say, "I know it all. Nothing more to learn."


But when you throw a little Latin into the mix, it's even worse. Without warning, you can find yourself staring at a word you've known all your life, wondering which verb form to use with it.

If algae is singular, it gets a verb conjugated in the singular: algae thrives. But if it's plural, it gets a verb conjugated in the plural: algae thrive.


Subject-verb agreement is an important part of an editor's job. So my confidence was rattled when recently I found myself dumbfounded by the pairing "algae thrives."

Luckily, answers are easy to find. Very easy. Just check a dictionary, which expressly states the plural form of every irregular noun, including those from Latin.

Here's what I learned in my dictionary: If you have just one little plant-like aquatic organism that's a member of any of several phyla, you have an alga. That's right, one alga. And how often does that happen?

No, the needy little alga doesn't like to spend time alone. So it seeks the company of many, many compadres, causing us to refer almost exclusively to the plural "algae."


First documented in the 1550s, alga, from Latin, meant seaweed. Since then, of course, it has been adopted in our ever-absorbent language to mean those tiny plant-like things we call algae.

Latin plurals are common in English, and they defy our standard system of adding S to form a plural: One cat, two cats. One house, two houses. One phenomenon, two — record scratch. Our neat little system of adding S gets tossed aside for rules based on a language most of us never studied. Surprisingly, we know a lot about it anyway.

We know one syllabus in the plural becomes two syllabi.

We know one cactus becomes two cacti.

We know one criterion becomes two criteria.

We know one nucleus becomes two nuclei.

Many presume that every word adopted from Latin forms its plural according to Latin rules. It's a bad assumption. Ever known anyone with an aquarium in his living room and another in the kids' room that he refers to collectively as "two aquaria"? If a difficult choice is compounded by another difficult choice, do you face "two conundra"?

When English adopts words from other languages, sometimes we adopt the foreign plural (panini), sometimes we don't (pizzas), and sometimes we go rogue and start using the plural as a singular (media, spaghetti).


Assuming that Latin words necessarily get Latin plurals can lead to silly mistakes, such as a debate that broke out a few years ago when the Toyota company held a survey to decide the plural of its Prius car. The Latin-derived "Prii" won. And the rest is forgotten history.

Almost unanimously, news media and English speakers ignored the directive. Priuses, they seemed to agree, was the natural plural. Most didn't know how right they were. The Latin word "prius" is an adjective or adverb meaning "prior." Adverbs don't have plural forms.

Consider an artist who sang two songs "beautifullys" and you'll get a sense of what I mean.

Adjectives in Latin do reflect the number of the nouns they describe, but the car name Prius functions as a noun. So it's just weird to first adopt an adjective as a noun (Hello, beautiful), then make it plural (Hello, beautifuls), then expect it to translate from a language that's been dead for centuries.

The lesson: If you want to form plurals well, you don't need to become fluent in Latin. Just remember that the rules were formed on a case-by-case basis, and that the answers are all in your dictionary.

JUNE CASAGRANDE is the author of "The Best Punctuation Book, Period." She can be reached at