If you’ve ever wondered about the plural of hippopotamus, you’re not alone. Many English learners and native speakers pause when they need to write more than one hippopotamus. Should you say hippopotamuses or hippopotami?
The answer is a little more interesting than you might expect because both plural forms are accepted in English. However, one is more common in modern usage, while the other has a classical feel. In this guide, you’ll learn the correct plural of hippopotamus, the difference between hippopotamuses vs. hippopotami, and when to use each one.
We’ll also explain the grammar behind the word, share clear examples, compare dictionary recommendations, and help you avoid common mistakes so you can use the right plural with confidence in everyday writing.
Quick Answer
The plural of hippopotamus can be hippopotamuses or hippopotami, and both forms are correct. However, hippopotamuses is the more common choice in modern English, while hippopotami comes from a classical Latin-style plural and is used less often. If you’re unsure which plural form of hippopotamus to use, hippopotamuses is the safest option for most writing.
Hippopotamus Plurals at a Glance (Comparison Table)
Before learning the grammar rule, here’s a quick comparison of the plural of hippopotamus. Both hippopotamuses and hippopotami are accepted in English, but they are not used equally.
Hippopotamuses is the preferred form in modern English and appears more often in books, newspapers, and everyday writing. Hippopotami follows a Latin-style pattern and is still considered correct, though it sounds more formal or traditional.
If you’re asking, “What is the plural of hippopotamus?” either word is correct, but choosing the right one depends on your audience and writing style. The table below makes the difference easy to understand.
| Singular | Plural | Correct? | Common Usage |
| Hippopotamus | Hippopotamuses | ✅ Yes | Most common in modern English |
| Hippopotamus | Hippopotami | ✅ Yes | Less common, classical style |
What Does “Hippopotamus” Mean?
A hippopotamus is a large, plant-eating mammal that lives in rivers and lakes across parts of Africa. The name comes from Greek words meaning “river horse,” although hippopotamuses are not closely related to horses.
In English grammar, hippopotamus is a singular noun used when talking about one animal. When referring to more than one, you need the correct plural form of hippopotamus. Many people wonder whether hippopotamuses or hippopotami is the better choice because both appear in dictionaries and books.
Understanding the meaning of the word makes it easier to learn its plural. Just as spelling questions like Pre-Existing or Preexisting depend on grammar rules, choosing the right plural also depends on accepted English usage.
What Is the Correct Plural of Hippopotamus?
The correct plural of hippopotamus can be either hippopotamuses or hippopotami. Both forms are accepted by major dictionaries and grammar experts. However, hippopotamuses is the form most people use in modern English because it follows the regular English rule of adding -es to nouns ending in -us.
Hippopotami is based on a traditional Latin-style plural and is still correct, although it appears less often in everyday writing. If you are writing for school, work, or a general audience, hippopotamuses is usually the safest choice.
If you’ve ever searched “how do you pluralize hippopotamus” or “is hippopotami correct,” the answer is simple—both are correct, but one is much more common today.
Hippopotamuses vs. Hippopotami: What’s the Difference?
The debate over hippopotamuses vs. hippopotami is mostly about style, not correctness. Both words describe more than one hippopotamus, but they have different backgrounds. Hippopotamuses follows modern English grammar and is widely used in newspapers, websites, classrooms, and everyday conversations.
Hippopotami, on the other hand, reflects a classical Latin-style ending that some writers prefer in formal or academic contexts. Most readers today are more familiar with hippopotamuses, making it the clearer option.
Similar language questions arise with everyday words, such as Buses or Busses, where one spelling is generally more common than the other. Choosing the more familiar form helps make your writing easier for readers to understand.
Why Does Hippopotamus Have Two Accepted Plurals?
Many English words have more than one accepted plural because they come from different languages. The word hippopotamus has Greek roots, but over time it became part of English, where different plural patterns were accepted.
One pattern creates hippopotamuses by adding -es, following standard English grammar. The other produces hippopotami, which reflects a traditional Latin-style ending that became popular in earlier English writing. This is why dictionaries recognize both forms today.
Knowing why there are two plural forms helps you understand that the difference is about language history rather than right or wrong. Modern English often accepts multiple forms, but one usually becomes more common through everyday use.
Which Plural Is More Common in Modern English?
If you’re wondering which plural is more common, the answer is hippopotamuses. It is the form you’ll see most often in modern books, newspapers, educational materials, and online articles. Because it follows a familiar English pattern, it sounds natural to most readers.
While hippopotami is still correct and appears in some formal or traditional writing, it is used much less frequently. For most situations, especially when writing for a broad audience, hippopotamuses is the better choice.
If your goal is clear communication, using the more familiar plural of hippopotamus helps readers understand your meaning immediately. Unless a style guide recommends otherwise, hippopotamuses is the preferred option in everyday English.
What Do Major Dictionaries Say?
If you want the most reliable answer, it helps to check trusted dictionaries. Major references like Cambridge Dictionary and Merriam-Webster recognize both hippopotamuses and hippopotami as correct plural forms.
However, many dictionary examples and modern writing sources use hippopotamuses more often because it follows regular English grammar. Hippopotami is also listed as an accepted form, especially because of its classical background. This means you don’t have to worry about choosing a “wrong” plural. Instead, think about your audience and writing style.
For school assignments, business writing, blog posts, and everyday communication, hippopotamuses is usually the easiest and clearest choice, while hippopotami adds a more traditional or formal touch.
Examples of Hippopotamuses and Hippopotami in Sentences
Seeing both plural forms in real sentences makes them easier to remember. Here are a few examples:
- The hippopotamuses gathered near the river before sunset.
- Visitors watched several hippopotamuses swimming together in the lake.
- The wildlife guide explained how hippopotami spend much of their day in the water.
- Researchers observed a group of hippopotami during their field study.
All of these sentences are grammatically correct. Even so, hippopotamuses sounds more natural in everyday English and is the form most readers expect. If you’re writing for a general audience, this version improves clarity. Hippopotami remains a correct choice for formal writing or when a classical style better fits your purpose.
Common Mistakes People Make
One common mistake is believing that only hippopotami is correct. In reality, both hippopotamuses and hippopotami are accepted by respected dictionaries. Another mistake is thinking that hippopotami is always the better or more educated choice.
While it has a classical feel, hippopotamuses is actually more common in modern English. Some writers also mix the two forms within the same article, creating an inconsistent writing style. It’s usually better to choose one form and use it throughout your work.
Finally, avoid guessing the plural based only on similar-looking words. English has many exceptions, so checking a trusted dictionary is always the safest way to confirm the correct plural of hippopotamus.
Similar Words with Multiple Accepted Plurals
The plural of hippopotamus is not the only word that gives English learners trouble. Several nouns have more than one accepted plural because of their history and how they entered the English language.
For example, appendixes and appendices are both correct, while cactuses and cacti, funguses and fungi, or curriculums and curricula are also accepted in many situations. Like hippopotamuses and hippopotami, one version often sounds more natural in everyday English, while the other has a more traditional or academic style.
Learning these patterns helps you understand that English grammar values both correctness and common usage, depending on the context and your audience.
Tips for Remembering the Correct Plural
A simple way to remember the correct plural of hippopotamus is to think about your readers. If you’re writing for everyday communication, choose hippopotamuses because it is the form most people recognize.
Remember that adding -es is a common English rule for many nouns, making this plural easy to recall. You can also remember that hippopotami is the more classical alternative, but it is less common in modern writing.
Reading books, news articles, and trusted grammar resources will help you become familiar with both forms. The more often you see these words in context, the easier it becomes to decide which plural form of hippopotamus best fits your writing.
FAQs
Is hippopotamuses correct?
Yes. Hippopotamuses is a correct plural and the most common form in modern English.
Is hippopotami correct?
Yes. Hippopotami is also correct and is recognized by major dictionaries.
Which plural should I use?
For most situations, hippopotamuses is the preferred choice because it is easier for readers to recognize.
Why are there two plural forms?
English accepts both forms because of the word’s history and the influence of different plural patterns.
What is the safest option for everyday writing?
If you’re unsure, choose hippopotamuses. It is widely understood and commonly used.
Conclusion
The plural of hippopotamus can be either hippopotamuses or hippopotami, and both forms are grammatically correct. The main difference is how often they are used. Hippopotamuses is the preferred choice in modern English because it follows familiar grammar rules and feels natural to most readers.
Hippopotami remains an accepted alternative with a more traditional and classical style. Knowing this difference helps you write with greater confidence, whether you’re working on a school paper, a professional document, or everyday content.
When in doubt, choose the form that best matches your audience and keeps your writing clear. Using the right plural consistently will make your work more accurate, readable, and easy to understand.