Plural of “fungus”

The plural of fungus is fungi (some dictionaries also accept funguses).

Why

"Fungus" is a direct Latin borrowing, and it kept the standard Latin second-declension -us to -i plural pattern, giving "fungi" (traditionally pronounced "FUN-jai" or "FUN-gee," with genuine disagreement over which pronunciation is more correct — both are widely used and accepted). This is the same pattern behind "cactus/cacti" and "nucleus/nuclei."

"Funguses" is a fully accepted, increasingly common regularized alternative, particularly in general and popular-science writing, while "fungi" remains the dominant form in mycology (the scientific study of fungi) and other technical biological contexts — again the same frequency-driven pattern where a word's formal/technical use anchors the classical plural while everyday use drifts toward the regular -s form. The adjective "fungal" (as in "fungal infection") is fully regular and shows no trace of the noun's Latin plural pattern, which is typical: English adjectives derived from Latin nouns with irregular plurals almost always regularize completely, since adjectives in English don't inflect for number the way nouns do.

Usage note

Either plural passes muster in ordinary writing: mycology journals and textbooks lean almost entirely on "fungi," whereas a gardening blog or casual nature piece can reach for "funguses" without anyone blinking. Popular culture and video games have also popularized "fungi" specifically as a flavor of monster or environment type (mushroom creatures, fungal forests), reinforcing the classical plural among a broad non-scientific audience who might otherwise never encounter Latin plural patterns in their everyday reading.

Popular field guides and nature documentaries have shifted heavily toward "fungi" specifically (rather than "funguses") over the last few decades, likely influenced by the rising public profile of mycology as its own respected scientific field rather than being treated as a minor branch of botany. The word itself is far older than the science built around it: "fungus" shows up in English medical and herbal writing as early as the 16th century, centuries before biologists formally split fungi off into their own separate kingdom, distinct from plants and animals, in the 20th century. Home-improvement and pest-control writing overwhelmingly favors "fungus" in the singular collective sense ("treat for fungus") over any plural form at all, since most everyday mentions describe an infestation generally rather than counting distinct organisms.

Common real mistakes

The pronunciation of "fungi" causes more genuine confusion than its spelling — both major pronunciations are attested in dictionaries, so neither is strictly an error, but mixing them up mid-conversation can sound inconsistent. A further genuine point: informal medical language for common fungal skin conditions ("athlete's foot," "ringworm") almost never uses the word "fungus" or its plural directly at all, reserving the more clinical vocabulary for doctors' notes and pharmaceutical labeling, while everyday conversation about fungal infections typically avoids the biological term entirely in favor of the condition's common name.

The wider pattern

This is the same -us/-i pattern behind "cactus/cacti," "nucleus/nuclei," "alumnus/alumni," and "radius/radii" — a family of Latin loanwords, mostly entering English through science and medicine, whose plural form tends to track how technical or how everyday the specific word has become over time.

Examples

• The forest floor was covered in a variety of fungi.
• Several funguses grew on the fallen log after the rain.
• Mycologists classify fungi separately from plants and animals.
• The damp basement had visible fungi growing along the wall.
• Some fungi are edible, while others are highly toxic.
• Researchers discovered three new species of fungi in the cave.
• The greenhouse battled a persistent fungus for weeks.
• Different fungi thrive in different soil conditions.
• A rare fungus was found growing on the old oak.
• The study catalogued fungi found in urban parks.
• A rare bright orange fungus grew along the fallen tree trunk.
• The mycologist photographed the unusual fungus for her research journal.