“Cacti” or “cactuses”: what’s the plural of cactus?
If you’re on a leisurely stroll through the desert terrain and spot a cactus …then there’s another—how would you describe what you saw? Would you use the word cacti or cactuses or …cactopodes?
The answer is that cactus has two accepted plurals: cacti and cactuses are both correct spellings to refer to more than one cactus.
The history of the cacti
Cactus comes from the Greek word, κακτος. Its first recorded use is by the Greek botanist Theophrastus, describing a spiny plant. Carl Linnaeus came up with the name for these spiked and leafless plants that we now call cactus, believing that the succulents were a long-distance relative of the Sicilian plant. This was in 1769, once the word had entered and evolved from Latin.
That’s the history of the word cactus, and despite being originally Greek, cactus still uses Latin suffixes to denote both singular and plural noun forms. There are still many commonly used Latin noun forms in English that follow the same pattern as cactus.
Think of other words in English like fungus, alumnus and syllabus: they all switch to “I” as a plural, the plural of fungus is fungi, alumnus is alumni and syllabus becomes syllabi. Cacti, likewise, is still accepted and recognized as a plural to mean more than one of these desert succulents.
Cactuses or cacti
Cactuses uses the standard Americanized plural noun form, and adds an -es to show a plural. This spelling is also accepted and widely used in conversation and writing.
What’s the takeaway on the correct plural of cactus? Well, the answer is that there are two correct ways to refer to more than one cactus: cacti and cactuses. One is not technically more correct or better than the other, but if you want to stick to the original Latin form, you can use cacti. The choice is ultimately yours to make; we’re just here as a helpful guide.
Words that end in -us
Cactus is an irregular plural noun that does not end in the typical -s/-es that regular plural noun forms take. This is probably why the plural of cactus is often confused, since its original plural form, cacti, is irregular in English and fairly uncommon. Still, cactus is not alone: fungus, alumnus, octopus, hippopotamus, all end in -us in their singular noun form. Likewise, each behaves the same in their plural forms, and substitutes the -us for -i: fungi, alumni, cacti, octopi (octopuses), and hippopotami (or hippopotamuses).
| singular | plural |
| cactus | cacti (or cactuses) |
| octopus | octopi (or octopuses) |
| radius | radi (or radiuses) |
| fungus | fungi (or funguses) |
| alumnus | alumni (or almunuses) |
| syllabus | syllabi (or syllabuses) |
Aside from being irregular plural noun forms, these words all share a common history and have a Latin origin. Latinate suffixes are words that derive from Latin rather than, say, Old English or Germanic languages (which make up the English language) and still imitate their Latin form.
Words like fungus, alumnus, cactus, and other similar structured words have kept their original Latin form in singular and plural nouns. That’s pretty incredible, and means that these words have been in use since roughly the early 16th century.
What are cactuses?
Cacti are:
any of a family (Cactaceae, the cactus family) of plants that have succulent stems and branches with scales or spines instead of leaves and are found especially in dry areas (such as deserts). (Merriam-Webster).
Examples of cacti/cactuses used in context
| Examples: “cacti” / “cactuses” used in sentences |
|---|
| The leafless, spiny stem is the characteristic feature of the majority of cacti. Almost all cacti are succulents, meaning they have thickened, fleshy parts adapted to store water. Cacti show a wide variety of growth habits, which are difficult to divide into clear, simple categories. The 1,500 to 1,800 species of cacti mostly fall into one of two groups of “core cacti“: opuntias (subfamily Opuntioideae) and “cactoids” (subfamily Cactoideae). |
Origin of the word cactus
c. 1600 from Latin cactus, from Greek kaktos, name of a type of prickly plant of Sicily (the Spanish artichoke), a “foreign word of unknown origin.”
Sources
- Hawkes, Michael W. “Cactus”. The Canadian Encyclopedia, 04 March 2015, Historica Canada. www.thecanadianencyclopedia.ca/en/article/cactus. Accessed 29 May 2025.
- “Cactus.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/cactus. Accessed 29 May. 2025.
- Wikipedia contributors. “Opuntioideae.” Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 1 Jan. 2025. Web. 29 May. 2025.
