What Is the Plural of Fungus?

The plural of fungus can be either fungi or funguses. Both forms are correct, but they are used in different contexts. Fungi is the standard plural in scientific and formal writing, following the Latin plural pattern. Funguses is the English plural form and is acceptable in everyday conversation and less formal writing. Your choice depends on your audience and the tone you need.

Quick Answer

• Fungi – Use in scientific, medical, or formal contexts. This is the preferred form in academic writing, textbooks, and professional reports.
• Funguses – Use in casual conversation, general writing, or when speaking with a non-specialist audience. It is less common but perfectly acceptable.

Understanding the Two Plurals

The word fungus comes from Latin, where it belongs to a group of nouns that end in -us and form their plural by changing -us to -i. This is the same pattern you see with words like alumnus (alumni) and cactus (cacti). Over time, English speakers have also created an English-style plural by simply adding -es to the end, giving us funguses.

In medical and biological writing, fungi is the standard. You will see it in research papers, clinical notes, and textbooks. In contrast, funguses appears more often in general-interest articles, patient education materials, and everyday speech. Neither is wrong, but using the wrong form in a formal document can make your writing seem less precise.

Comparison Table: Fungi vs. Funguses

Natural Examples

Seeing both forms in real sentences helps you understand when to use each one.

• Formal / Scientific: “The patient’s infection was caused by two different fungi, requiring a combination of antifungal medications.”
• Informal / Conversation: “I think there are a few funguses on the old bread in the fridge.”
• Email to a colleague: “Please check the culture results for any fungi before we proceed with treatment.”
• Text to a friend: “The mushrooms in the yard look weird—are they funguses?”

Common Mistakes

Even native speakers sometimes make errors with this word. Here are the most frequent mistakes and how to avoid them.

• Using “fungi” as a singular: “This fungi is dangerous.” → Incorrect. Fungi is plural. The singular is fungus. Correct: “This fungus is dangerous.”
• Adding an extra “i”: “fungii” → Incorrect. The Latin plural is fungi, not fungii. There is no double “i”.
• Using “funguses” in a formal paper: While not grammatically wrong, it may look out of place in a scientific journal. Stick with fungi for formal writing.
• Confusing “fungus” with “mold” or “mildew”: All are types of fungi, but they are not interchangeable in medical contexts. Use the specific term when possible.

Better Alternatives and When to Use Them

Sometimes you may want to avoid the plural altogether or use a more precise term. Here are some alternatives.

• Fungal species – Use when you need to be specific about different types. Example: “Several fungal species were identified in the study.”
• Fungal infections – Use in medical contexts instead of “fungi” when referring to diseases. Example: “The patient has recurrent fungal infections.”
• Molds – Use when the fungi are specifically molds. Example: “The bathroom has molds growing in the corners.”
• Yeasts – Use for single-celled fungi. Example: “The lab cultured yeasts from the sample.”
• Mushrooms – Use for the visible fruiting bodies of certain fungi. Example: “We found several mushrooms in the forest.”

When you are writing a formal report, fungi is usually the best choice. In a patient education handout, you might use funguses or switch to a more descriptive term like “fungal infections” to be clearer.

Mini Practice: Test Your Knowledge

Choose the correct form for each sentence. Answers are below.

1. The lab technician identified three different ______ in the culture. (fungi / funguses)
2. There are several ______ growing on the old wood in the shed. (fungi / funguses)
3. This ______ is commonly found in soil. (fungi / fungus)
4. The doctor explained that some ______ can cause skin infections. (fungi / funguses)

Answers:

1. fungi – Formal, scientific context.
2. funguses – Informal, everyday context.
3. fungus – Singular form is needed here.
4. fungi – Medical context, formal tone.

FAQ: Common Questions About the Plural of Fungus

Is “fungi” always correct?

Yes, fungi is always correct in formal and scientific writing. It is the standard plural used in medical and biological literature. In very casual contexts, funguses is also acceptable, but fungi is never wrong.

Can I use “funguses” in a medical report?

It is not recommended. Medical reports and academic papers typically follow Latin plural conventions. Using funguses in such documents may appear unprofessional or imprecise. Stick with fungi for professional writing.

What is the singular of “fungi”?

The singular is fungus. Remember that fungi is already plural, so do not use it with a singular verb. For example, say “This fungus is common” not “This fungi is common.”

Are there other words like “fungus” that have two plurals?

Yes. Many Latin-derived words have both a Latin plural and an English plural. Examples include cactus (cacti / cactuses), syllabus (syllabi / syllabuses), and focus (foci / focuses). The Latin plural is usually preferred in formal contexts, while the English plural is fine in everyday use.

Final Tip for Learners

When you are writing an email, a report, or a study note, think about your reader. If you are writing to a doctor, a professor, or a scientist, use fungi. If you are writing to a friend, a patient, or a general audience, funguses is perfectly fine. The most important thing is to be consistent within your document. Do not switch between the two forms in the same piece of writing.

For more help with medical plurals, visit our Common Plural Forms section or check our FAQ page. If you have a specific question, feel free to contact us.