Cacti or Cactuses: What’s the Plural of Cactus?
The Blue Book of Grammar and Punctuation
Cacti or Cactuses: What’s the Plural of Cactus?
Suppose you are writing a science-fiction novel in which spiky plants come to life in the desert. They uproot themselves and begin pursuing your hero. As they bear down, how would you refer to them: as cacti, cactuses, or something else?
In other words, what’s the plural of cactus?
The Plural of Cactus
The origin of the word cactus dates to 1600, when it was used to describe a prickly plant of Sicily, the Spanish artichoke (known as a cardoon or artichoke thistle). Although the artichoke is prickly, it is not similar in appearance to the cactus we typically envision in America.
The use of the word cactus in English began in 1769 to describe the green, leafless plants of the American desert. The most common cactus that we think of in the U.S. is the saguaro cactus of the Southwest.
Cactus has a Latin root that derives from the plural cacti, which makes cacti the technically proper plural spelling. If you want to stay on the right side of the rulebook, you can refer to more than one cactus as cacti.
At the same time, as cactus was assimilated into English, it inevitably received English treatment, which often pluralizes a word by adding s or es. As a result, cactuses became an accepted plural as well.
For the purpose of this discussion, we would typically identify cacti as proper plural use in daily formal writing and cactuses as acceptable use in conversational or other less formal communication. If your writing is influenced by a teacher, a departmental preference, or a particular style guide, you can refer to it for guidance as well.
Why It’s So Hard to Learn the Plural Versions of Some English Words
Some words can tend to inspire more discussions and questions than others. That is because it’s easy to specify their singular form, but once we make them plural, things can get hazy in establishing any kind of consistency.
Examples
foot (sing.) vs. feet (plural)
knife (sing.) vs. knives (plural)
hero (sing.) vs. heroes (plural)
die (sing.) vs. dice (plural)
goose (sing.) vs. geese (plural)
moose (sing.) vs. moose (plural)
These illustrate how rules can change from one word to the next. As we’ve touched on, to form the plural of an English word, we often simply add an s or an es, but as shown in our examples, this does not always apply.
In many instances it’s because a particular word or phrase has its origin in another language. Modern American English is a blend of terms from older English, Latin, Greek, French, Spanish, German, and so on. It’s no wonder that we have so many nouns that are pluralized in different ways. Why do we have one goose and two geese but one moose and two moose?
In some cases we might also notice that a certain word looks or sounds wrong if we follow our normal s or es pluralization. For instance, tooth becomes teeth because “tooths” would sound awkward to the American ear as well as be more difficult to enunciate.
For additional study of this topic, you can review our articles Irregular Plurals and Irregular Plural Nouns.
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You say “tooth becomes teeth because ‘tooths’ would sound awkward to the American ear”… But the plural of “truth” is “truths,” same pronunciation as “tooth” give or take the “r.”
The English habit of changing the vowel in plurals comes from German, or Germanic languages. Interesting, that works for in modern German for mouse (Maus/Mäuse) and teeth (Zahn/Zähne) too.
What would be the plural possessive form of cactus? Cacti’s, cactis’ or something else?
Since “cacti” is already plural, it would be “cacti’s” (and, alternately, “cactuses'”).
So is Cactus Island then a misnomer? There are many cacti on the island, not just one.
The word cactus is used as an adjective to describe “island.” See our post Apostrophes and False Possessives.
How does the fact there is a plural root make that the proper form in English? To note: the OED doesn’t recognize cacti as an English word at all.
More than half of English words have roots in Latin or Greek. Our current use of the singular word “cactus” has a Latin origin from the plural Latin word “cacti.” Maintaining the Latin form makes it proper in formal writing. As the article points out, over time we have also assimilated the word into English by giving it a more contemporary treatment, “cactuses,” which is less formal but still acceptable.
Where OED focuses on British English, we concentrate on American English; the Oxford Advanced American Dictionary does recognize “cacti.”