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What’s the Plural of Hippopotamus?

The short answer is that both hippopotamuses and hippopotami are correct plurals for this barrel-bodied and rotund mammal: the hippopotamus.

What’s the plural of “hippopotamus”?

The short answer is that both hippopotamuses and hippopotami are correct plurals for this barrel-bodied and rotund mammal: the hippopotamus.

What are hippos?

Hippopotamus, more commonly referred to as hippos, are a semi-aquatic mammal native to Sub-Saharan Africa. There are two living species of the hippo: the pygmy hippo (Choeropsis liberiensis), and the common hippo (Hippopotamus amphibius.)

Are hippos the same as rhinoceros?

While both mammals are native to Africa, are massive and are herbivores, the rhinoceros and hippopotamus are different animals, with several distinct differences and markers that tell them apart. Rhinos are the second largest land mammal next to elephants, on average they are larger than hippos (hippos are the third largest land mammal, #TheMoreYouKnow @grammar_flex on twitter.)

Why is hippopotami the plural of hippopotamus?

Remember, people: English, as a language, has its roots in other languages. We’re talking Greek, Latin, Dutch, German, Old Norse, Old Frisian; in some cases Spanish, Portuguese, and so on and so forth. If you’re curious to read more about the origins  of English and its effect on noun forms, check out GFlex’s post on irregular and regular nouns. To get back to topic, what’s the deal with the word hippopotamus, and why are there two plural forms; i.e., hippopotamuses and hippopotami? Lastly, what’s the deal with ‘hippopotami,’ ?

Though the word hippopotamus has Greek origin, through Latin influences and language, hippopotamos from the Greek became hippopotamus in Late Latin. The difference is subtle: Latin suffixes for singular nouns commonly end in -us. See, for example, cactus, fungus, alumnus, syllabus, and so on. Likewise, as a plural noun, each replaces the -us with the Latinate -i. See the following irregular Latinate plural nouns:

hippopotamushippopotamuses (or hippopotami)
octopusoctopi (or octopuses)
radiusradi (or radiuses)
fungusfungi (or funguses)
alumnusalumni (or almunuses)
syllabussyllabi (or syllabuses)
Latin nouns ending in –us/-i. Chart by Grammarflex.

What’s the singular of hippopotamus?

It’s just hippopotamus. Most commonly, people prefer hippo/hippos because it’s one syllable as opposed to five.

Other irregular plural nouns

Hippopotamus is an irregular plural noun that does not end in the typical -s/-es that regular plural noun forms take.

Origin of the word hippopotamus

When in doubt—look to the language of origin. Hippopotamus comes from the Greek word, hippopotamos, “riverhorse.”  Turns out Ancient Greek enjoyed their compound words too: hippopotamus is a compound from the Greek word hippos “horse” + potamos “river, rushing water.” This makes sense, since they partly live in the water.

Examples of hippopotamus/hippo used in context

1. The hippo is considered to be extremely aggressive and has frequently been reported charging and attacking boats.

2. Aside from elephants and rhinos, the hippopotamus is the largest land mammal.

3. In 1987, the Toledo Zoo saw the first underwater birth by a captive hippo.

4. The exhibit was so popular, the logo of the Toledo Zoo was updated to feature the hippos.

5. Hippos generally breed well in captivity; birth rates are lower than in the wild, but this can be attributed to zoos’ desire to limit births, since hippos are relatively expensive to maintain.

Examples of hippopotami/hippopotamuses

1. Ostriches are found in the open plains; the rivers swarm with crocodiles, but hippopotami are rare.

2. Crocodiles and two kinds of hippopotami, the ordinary and a pygmy variety, are found in the rivers.

3. The rivers in the tropical zone abound with hippopotami and crocodiles, the former entirely confined to Africa.

4. Hippopotami are found on the coast, and alligators are common in the rivers and lagoons of the low country.

5. Hippopotami are still found in the Umgeni river and crocodiles in several of the coast streams. Leopards and panthers are found in thickly wooded kloofs.

Collective nouns for hippopotami

Hippopotami in groups are called a ‘bloat‘, as in, ‘a bloat of hippos emerged from the river.’ Male hippos are typically referred to as a bull; females are cows, and baby hippos are calf.

Rome wasn’t built in a day; and likewise, grammar cannot be learned overnight. Take some time to keep learning, improve your writing, and maybe have some fun while you’re at it!


  1. Wikipedia, hippopotamus.
  2. Hippo-vs-rhino
  3. Origin of hippo the word
  4. Sentences with hippopotami
  5. Hippopotami collective terms

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