Plural of Hippopotamus

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The plural of hippopotamus is hippopotamuses or hippopotami.

The Plural of Hippopotamus

The plural of hippopotamus is hippopotamuses or hippopotami.
  • Hippopotamuses live in groups of up to thirty.
  • Though they are bulky animals, hippopotami can gallop at 19 mph on land.
The noun hippopotamus has a Latin root, which is the derivation of the plural hippopotami. However, hippopotamuses (which adheres to the standard rules for forming plurals) has become marginally more common than hippopotami.

Of note, the shortened version hippos is often used in informal writing to avoid to making a decision on hippopotamuses and hippopotami.

The table below shows the standard rules for forming the plurals of nouns in English.

Type Example of Type Forming the Plural Plural
Most Nouns lamp
scythe
add s lamps
scythes
Noun Ending s, sh, ch, x or z hippopotamus
dress
add es hippopotamuses
dresses
Nouns ending [consonant] o hero
zero
tomato
add either s or es
(There are no rules for this - you have to know.)
heroes
zeros
tomatoes
Nouns ending [vowel] o patio
ratio
add s patios
ratios
Nouns ending [consonant] y story
penny
change the y to an i and add es stories
pennies
Nouns ending [vowel] y donkey
chimney
add s donkey
chimneys
Nouns ending f or fe dwarf
hoof
ves and/or s
(There are no rules - you have to know.)
dwarfs
hooves or hoofs
Exceptions man
louse
some nouns undergo a vowel or letters change men
lice
More exceptions salmon
sheep
some nouns do not change at all salmon
sheep
Foreign rulings hippopotamus
medium
some nouns adopt foreign rulings hippopotami
media

Why Is There Confusion over the Plural of Hippopotamus?

Confusion arises over the plural of hippopotamus because its original plural form (hippopotami) derives from Latin and native English speakers are drawn to hippopotamuses, which adheres to the standard ruling for forming plurals.

Hippopotamuses is the more common plural of the two. (See the difference in Google's Ngram Viewer.)


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