What’s the plural of “fungus”?
Both funguses and fungi are acceptable plurals to refer to this widespread category species and organism.
What are fungi/funguses?
Brittanica online defines fungi as:
Any of about 144,000 known species of organisms of the kingdom Fungi.Many people think of fungus as mushrooms, in conversation and informal speech.
Other terms people use to mean fungi include mildew, mold, mushroom, rusts, yeast, or smut.
Is fungus/fungi a regular or irregular plural noun?
The Americanized plural, funguses, is a regular plural noun form since it uses the -es. That said, funguses most likely came to be accepted over time due to the widespread misuse of the correct and original plural form of fungus, i.e., fungi.
While an irregular plural in English, fungi are not alone: octopus, alumnus, cactus, hippopotamus and the like all share the same (or similar) ending singular and plural forms. See the following chart that illustrates both:
| Singular | Plural |
|---|---|
| cactus | cacti (or cactuses) |
| octopus | octopi (or octopuses) |
| radius | radii (or radiuses) |
| fungus | fungi (or funguses) |
| alumnus | alumni (or alumnuses) |
Fungi is the original Latinate plural, and uses one of the distinct Latin suffixes, i.e., -i. Likewise, the fungi‘s companion nouns similarly use their Latin (or near Latin) words/forms in Modern English today.
Cactus, octopus, alumnus, syllabus, and so on all use the Latinate -i suffix, and have conserved their form since its inception (or near inception) as a word/noun.
Therefore, fungi is irregular as a plural, but technically so are cacti, octopi, alumni, syllabi and any other Latin plural that uses its early spelling. So, if you've ever wanted to say you know some Latin...
Examples of fungus in used sentences
| Examples of “fungus” | Examples of “fungi” |
|---|---|
| Ultimately, we are left in the untenable position of admitting that there is no definition in general use for the word “fungus.” | The Fungi are the great saprophytes, the master recyclers. |
| Grapes attacked by the fungus; the fruit becomes black, hard and shrivelled. | The rich colour of the grass is due to the fertilizing quality of the decaying fungi, which are peculiarly rich in nitrogenous substances. |
| The Latin word for mushroom, fungus (plural fungi), has come to stand for the whole group. | Fungi draw their nutrition from decaying organic matter, living plants and even animals. |
| The mushroom is just the part of the fungus we see above ground which is also known as the fruiting body. | Fungi reproduce through spores, which are like asexual plant seeds. |
| Many of these fungus-like organisms are included in the kingdom Chromista. | Examples of fungi are yeasts, rusts, stinkhorns, puffballs, truffles, molds, mildews and mushrooms. |
| The study of fungi is known as mycology—a broad application of the Greek word for mushroom, mykēs. |
Origin of the word fungus
From Latin fungus (same spelling and meaning). Believed to be connected to the Ancient Greek sphongos (“sponge”).
Practice: Latin nouns
The forest was teeming with unusual ______.
She identified a rare ______ in her backyard.
Several types of ______ can be harmful to crops.
The desert is home to many ______.
The students compared the ______ for each course they were taking.
FAQs
What are the plural forms of fungus?
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Which fungus plural is irregular?
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Which plural form is the original Latin?
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How should I use fungus plurals?
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What plural fungus mistakes are common?
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Sources
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1. The Editors of Encyclopaedia Britannica. "rust". Encyclopedia Britannica, 2 Jun. 2025, https://www.britannica.com/science/rust. Accessed 21 August 2025.
Yash, D. "How to Use Fungus Plural (Explained, With Example)." Grammarflex, Aug 24, 2025, https://grammarflex.com/fungus-plural/.
