Plural of Hippopotamus: Hippopotamuses or Hippopotami?

Last updated: November 9, 2026 at 2:39 pm by info.behlolpur@gmail.com

Have you ever wondered what to call more than one hippopotamus? The word itself is quite a mouthful, and its plural form can be confusing. You might have seen different spellings in books, articles, or everyday conversations and wondered which one is correct.

The good news is that the plural of hippopotamus can be hippopotamuses or hippopotami. Both forms are grammatically correct, but they have slightly different origins and usage patterns. Understanding the difference will help you choose the right word without second-guessing yourself.

In this guide, I’ll explain both plural forms, show you how to use them in sentences, and explore their origins. Whether you’re a student, a writer, or simply curious about English grammar, you’ll find the answer easy to understand.

What Is the Plural of Hippopotamus?

The plural of hippopotamus is hippopotamuses or hippopotami. Both forms are accepted in English, but hippopotamuses follows the regular English plural pattern.

Best choice: Use hippopotamuses when you want a straightforward, standard plural. Choose hippopotami when it suits your style or context. In casual writing, hippos is also natural.

Hippopotamuses or Hippopotami: What’s the Difference?

Both hippopotamuses and hippopotami mean more than one hippopotamus. The difference comes from their plural formation.

Hippopotamuses: The Regular English Plural

English usually forms the plural of many nouns by adding -s or -es. The word hippopotamus follows this familiar pattern:

• One hippopotamus
• Two hippopotamuses
• Several hippopotamuses

This form is easy to recognize and works well in school assignments, reports, articles, and everyday conversation.

Examples:

• The wildlife park cares for six hippopotamuses.
• Several hippopotamuses gathered near the lake.
• Researchers observed hippopotamuses during the dry season.
• The zoo introduced two young hippopotamuses to the public.

Hippopotami: The Traditional Alternative

Hippopotami is another accepted plural. Its ending may look like the traditional plural pattern found in some Latin-derived words, which is why many English speakers recognize it as a formal or scholarly-sounding alternative.

However, the history of hippopotamus is more complicated than simply adding a Latin plural ending. The word came into English through Latin from Greek. It is not a straightforward classical Latin noun that requires the ending -i.

You can use hippopotami without making a grammatical error, but hippopotamuses is generally the simpler default.

Examples:

• The naturalist watched several hippopotami from a safe distance.
• A group of hippopotami rested in the shallow water.
• The illustrated guide featured hippopotami from different regions.

Which Form Should You Use?

For most modern writing, choose hippopotamuses. It follows a familiar English rule and makes the plural immediately clear.

Use hippopotami if you prefer the traditional alternative or if it fits the tone of your writing. The important point is consistency: choose one form and use it throughout the same piece.

Why Is the Plural of Hippopotamus Hippopotami?

The form hippopotami is often associated with the Latin plural ending -i. That association explains why it looks familiar, but it does not tell the whole story.

The English word hippopotamus came through Latin from the Ancient Greek word hippopotamos. The original Greek plural was hippopotamoi. English later developed the regular plural hippopotamuses alongside the traditional alternative hippopotami.

The word itself has an interesting meaning. Its Greek roots are:

• Hippos: Horse
• Potamos: River

Together, they form the meaning river horse, a reference to the animal’s close association with rivers and other freshwater habitats.

This history helps explain why the word has more than one plural form. It does not mean that hippopotamuses is incorrect or that English speakers must use hippopotami.

Can You Use Hippos as the Plural of Hippopotamus?

Yes. Hippos is the correct plural of hippo, which is a shortened, informal form of hippopotamus.

People often use hippo because the full animal name is long. The shorter word sounds natural in conversation, children’s books, wildlife programs, and general-interest writing.

Compare these sentences:

• The hippopotamuses spent most of the afternoon in the water.
• The hippos spent most of the afternoon in the water.

Both sentences are correct. The first uses the full animal name, while the second uses its informal short form.

Remember that the plural is hippos, not hippoes. The word takes a simple -s ending.

How Do You Pronounce Hippopotamus and Its Plurals?

The word hippopotamus has five syllables, so it can take a little practice to pronounce. The plural forms add different endings.

Here are the common US pronunciations:

The stress in hippopotamus falls on the pot part of the word. Listening to a dictionary audio recording can help you hear the difference between the plural endings.

Hippopotamus in Example Sentences

Examples make it easier to see how each form works in real writing. Notice how the sentence changes depending on whether you mean one animal or several.

Examples With Hippopotamus

• A hippopotamus surfaced beside the riverbank.
• The young hippopotamus stayed close to its mother.
• A hippopotamus can open its mouth surprisingly wide.
• The wildlife photographer waited patiently for the hippopotamus to emerge.
• Our science class learned about the hippopotamus and its natural habitat.

Examples With Hippopotamuses

• Several hippopotamuses gathered in the shallow river.
• The sanctuary provides a protected habitat for its hippopotamuses.
• Researchers studied how hippopotamuses behave in groups.
• Two hippopotamuses rested near the muddy bank.
• The documentary showed hippopotamuses moving through the water at sunset.

Examples With Hippopotami

• The guide described the behavior of hippopotami in the wild.
• Several hippopotami appeared near the edge of the lake.
• The book included illustrations of hippopotami in their natural habitats.
• The researchers recorded observations of hippopotami during the expedition.

Examples With Hippos

• The children watched the hippos swim at the zoo.
• Hippos spend much of the day in or near water.
• We spotted three hippos during the wildlife tour.
• The nature program showed hippos grazing after sunset.

Common Mistakes When Using the Plural of Hippopotamus

Even familiar animal names can cause confusion when their plurals have more than one accepted form. Avoid these common errors.

1. Thinking Hippopotami Is the Only Correct Form

Some people assume that hippopotami must be correct because it resembles traditional Latin plurals. However, hippopotamuses is also correct and is the regular English plural.

Correct: The zoo has four hippopotamuses.

Also correct: The zoo has four hippopotami.

2. Treating Hippopotamuses as Incorrect

The ending -es follows a normal English plural pattern. There is no grammatical reason to reject it.

Correct: Several hippopotamuses were resting in the water.

3. Writing Hippoes Instead of Hippos

The shortened word hippo forms its plural by adding -s. It does not need an extra syllable or an -es ending.

Incorrect: The hippoes swam across the pool.

Correct: The hippos swam across the pool.

4. Confusing a Plural With a Possessive

An apostrophe does not make a noun plural. It usually shows ownership or a relationship.

• Hippopotamuses: More than one animal.
• Hippopotamus’s: Something belonging to one hippopotamus.
• Hippopotamuses’: Something belonging to multiple hippopotamuses.

For example:

• The hippopotamuses are eating.
• The hippopotamus’s habitat is near the river.
• The hippopotamuses’ enclosure needs cleaning.

Frequently Asked Questions

1. What is the plural of hippopotamus?

The plural is hippopotamuses or hippopotami. Hippopotamuses is the regular English form and the best default for most writing.

2. Is hippopotami grammatically correct?

Yes. Hippopotami is an accepted alternative plural of hippopotamus. It is not a mistake, although hippopotamuses is the more straightforward regular English form.

3. Is hippopotamuses or hippopotami more common?

Hippopotamuses is generally preferred as the regular English plural. Major dictionaries list both forms, so either can be used correctly.

4. Can I say hippos instead of hippopotamuses?

Yes. Hippos is the plural of hippo, an informal shortened form of hippopotamus. It is especially common in casual conversation and general-interest writing.

5. What is the plural of hippo?

The plural of hippo is hippos. You do not add -es to this shortened word.

6. Why does hippopotami end in -i?

The ending resembles a traditional plural pattern associated with Latin words. However, hippopotamus came through Latin from Greek, and hippopotami is an established alternative rather than a required classical Latin plural.

7. What is the origin of the word hippopotamus?

The word came into English through Latin from the Greek hippopotamos. Its Greek roots mean horse and river, giving the word the literal sense of “river horse.”

8. Is hippopotamus singular or plural?

Hippopotamus is singular when referring to one animal. For more than one, use hippopotamuses or hippopotami. The shorter plural hippos is also correct when using hippo.

Conclusion

The plural of hippopotamus can be hippopotamuses or hippopotami. Both forms are correct, but hippopotamuses is the regular English plural and the safest choice for most writing. You can also use hippos as the informal plural of hippo.

When in doubt, choose hippopotamuses. It is clear, familiar, and follows a standard English plural pattern.

Daniel Carter

I am Daniel Carter, a grammar enthusiast and language educator with over 10 years of experience helping students and professionals improve their English writing and communication skills. I enjoy simplifying complex grammar rules into easy-to-understand lessons that anyone can follow. My goal is to help learners write with confidence, avoid common mistakes, and develop strong communication skills for academic and professional success. I regularly create practical grammar guides, writing tips, and language resources that make learning both enjoyable and effective.

Books: Mastering English Grammar and The Complete Guide to Better Writing