Plural of Hippopotamus: What Is the Correct Form?
Plural of hippopotamus: what is the correct form? The standard modern plural is hippopotamuses, made by adding es to the singular, just like bus becomes buses. Hippopotami is also listed in dictionaries as an accepted plural, but it is the classical Latin style form, and most style guides prefer hippopotamuses in everyday writing. The plural of the short form hippo is simply hippos. Test your sentence with our free Grammar Checker and Spelling Quiz, and use the add es test below when the two plurals feel equal.
The word comes from the Greek for “river horse,” from hippos meaning horse and potamos meaning river, and it reached English through Latin. That mixed history is why two plurals exist at all. Our leafs or leaves guide shows the same pattern for another word where the plural follows a rule that is easy to miss.
Quick answer
Write hippopotamuses in almost every sentence. It is the usual plural in modern English, the form most newspapers use, and the form Garner’s Modern American Usage recommends. Use hippopotami only for a classical or playful tone, and write hippos for the plural of hippo.
Memory trick: Hippopotamus ends in s, so add es, just like bus to buses and class to classes. Say “hippopotamus-es” out loud, and the plural builds itself.
When to use hippopotamuses
Use hippopotamuses in school essays, news articles, science writing for general readers, and everyday conversation. It follows the regular English rule for nouns that end in s, sh, ch, x, or z: add es to make the plural. Dictionaries list it first, and it is the form readers meet most often, so it never looks strange or old fashioned. Quick and Dirty Tips on the plural of hippopotamus reaches the same verdict: both plurals appear in dictionaries, but hippopotamuses is the best choice, and it appears more often in books and newspapers.
✓ Three hippopotamuses rested in the river all afternoon.
✓ The zoo cares for two hippopotamuses in the new enclosure.
✓ Hippopotamuses spend most of the day in the water.
✓ A group of hippopotamuses is called a bloat or a pod.
✓ The river is home to many hippopotamuses.
✓ Young hippopotamuses stay close to their mothers.
The regular plural also matches how English treats similar words. Octopus becomes octopuses, virus becomes viruses, and bus becomes buses, and hippopotamus follows the same path. When a word has lived in English for centuries, the English plural usually wins over the foreign one, and hippopotamuses is the clear winner in modern books and newspapers.
Zoo guides, wildlife documentaries, and school textbooks all use hippopotamuses, because it is the form children and general readers understand at once. A documentary narrator who says “hippopotamuses” never has to explain the word, while hippopotami would stop some listeners and make them wonder whether they heard it right. That instant clarity is the real reason the regular plural wins: it lets the sentence carry the facts instead of the spelling.
✓ The guide told visitors that hippopotamuses sleep under water.
✓ The textbook explains how hippopotamuses keep cool in the river.
✓ The documentary filmed hippopotamuses at dawn.
✓ Hippopotamuses can weigh more than a small car.
When hippopotami appears
Use hippopotami when you want a classical, literary, or playful tone, or when you write for an audience that enjoys the Latin style plural. It still appears in dictionaries and in older books, and it is not wrong, but it is less common today. The New York Times has not used hippopotami since the 1930s, which shows how far the regular plural has pulled ahead in modern writing.
✓ The old poem spoke of hippopotami in the Nile.
✓ The naturalist wrote of hippopotami wallowing at dusk.
✓ In the story, the hippopotami guarded the river crossing.
✓ The museum label listed hippopotami among the river animals.
Think of hippopotami as the formal dress version of the plural: correct, but more dressed up than the occasion needs. In a joke, a poem, or a quiz about tricky plurals, it works well. In a school essay or a news report, hippopotamuses reads more naturally. Our heros or heroes guide shows the same es ending rule for another word where the plural hides in the spelling.
Crossword setters and quiz shows love hippopotami, because it is the answer that tests whether you know the classical plural. That is also why it survives in print: it is a useful word for word games, even though everyday writing has moved on. If you meet it in a puzzle or a poem, enjoy it, and if you meet it in an essay, switch it to hippopotamuses unless your teacher asked for the classical form.
✓ The crossword clue asked for hippopotami, nine letters.
✓ The quiz show host read out hippopotami as the trick answer.
✓ The quiz asked whether hippopotami or hippopotamuses was correct.
✓ Both hippopotami and hippopotamuses appear in the dictionary.
The tricky exceptions
Hippopotami is a hypercorrection, not a true Latin plural
Here is the twist that most guides miss: hippopotamus comes from Greek, not Latin, so the Latin style plural hippopotami is technically a hypercorrection. The word entered English through Latin, which is why the Latin ending feels natural, but the Greek root never had an i plural. That is why modern style guides call hippopotamuses the better choice, even while dictionaries keep hippopotami as an accepted variant.
✓ Greek root: hippos plus potamos, meaning river horse.
✓ Modern choice: hippopotamuses, the English plural.
The plural of hippo is hippos, never hippoes
The short form hippo follows the simplest rule of all: add s, and stop. Write hippos for two or more hippos, and never write hippoes, which is a common overcorrection. The same rule covers other short forms, such as rhino to rhinos, so the pattern is easy to remember once you see it. Our buses or busses guide shows the same single s versus double s question for another short plural.
✓ Two hippos played in the shallow water.
✗ Two hippoes played in the water. (Wrong: use hippos)
A group of hippopotamuses is a bloat or a pod
A group of hippopotamuses has two accepted collective nouns: a bloat and a pod. Bloat fits the animal well, since hippopotamuses spend their days floating with most of their bulk under water, and pod is the same word used for whales and dolphins. Either word is correct, so pick the one your reader will understand, and use the plural hippopotamuses with it.
Bloat is the more vivid of the two words, and it appears in most modern animal guides, while pod is the older and more general word for a group of water animals. Some guides use bloat for hippopotamuses on land and pod for those in the water, but no strict rule separates them, so either word works in any sentence about a group. What matters is the plural that follows: a bloat of hippopotamuses, never a bloat of hippopotamus.
✓ A bloat of hippopotamuses basked on the muddy bank.
✓ The pod of hippopotamuses moved slowly down the river.
✓ A bloat of hippopotamuses filled the river bend.
✓ A pod of hippopotamuses rested near the bank.
Hippopotamus plurals at a glance
| Form | Type | When to use it |
|---|---|---|
| hippopotamuses | English plural | Standard choice, all modern writing |
| hippopotami | Classical plural | Literary, playful, or older style only |
| hippos | Plural of hippo | Casual writing, the short form |
| hippoes | Spelling error | Never correct |
| hippopotamus | Singular | One animal only |
| bloat / pod | Collective noun | A group of hippopotamuses |
Quick practice
Choose the correct form for each sentence:
- Three ___ rested in the river. (hippopotamus / hippopotamuses / hippopotami)
- The plural of hippo is ___. (hippos / hippoes / hippopotami)
- A ___ of hippopotamuses filled the river. (bloat / bloats / bloating)
- Which plural does Garner’s Modern American Usage recommend? (hippopotami / hippopotamuses / hippos)
Answer key:
- 1. hippopotamuses (the standard modern plural)
- 2. hippos (add s to the short form, never es)
- 3. bloat (a bloat of hippopotamuses is the collective noun)
- 4. hippopotamuses (the guide recommends the English plural)
Frequently Asked Questions
What is the plural of hippopotamus?
The plural of hippopotamus is hippopotamuses, and hippopotami is also accepted. Hippopotamuses is the standard modern form, and it is the one most style guides recommend.
Is hippopotami wrong?
No, hippopotami is not wrong, since dictionaries list it as an accepted plural. It is simply less common today, and it suits a classical or playful tone better than everyday writing.
What is the plural of hippo?
The plural of hippo is hippos. Add s to the short form, and never write hippoes, which is a spelling error.
Final Thoughts
Hippopotamuses is the plural to use in almost every sentence, because it follows the regular English rule, it is the form dictionaries list first, and it is the form modern newspapers and style guides prefer. Hippopotami stays correct as a classical variant for poems, jokes, and older writing, and hippos covers the short form with a simple s. Remember the river horse root, add es to the long word and s to the short one, and the plural takes care of itself.
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