Plural of Virus

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The Quick Answer
The plural of virus is viruses.

The Plural of Virus

The plural of virus is viruses.
  • Viruses are found in almost every ecosystem on Earth.
  • Viruses are considered by some to be a life form, because they carry genetic material and can reproduce.
The noun virus has a Latin root, but is one of the few nouns that has no plural in Latin. It occurs only in the singular. The English plural viruses (which adheres to the standard rules for forming plurals) is the only way to make the noun virus plural.

The noun virus adheres to the standard rules for forming the plurals of nouns in English (shown in the table below).

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The Standard Rules for Forming the Plurals

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 virus
dress		 add es viruses
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 donkeys
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 fungus
medium 		some nouns adopt foreign rulings fungi
media

Why Is There Confusion over the Plural of Virus?

Viruses is the only way to make the noun virus plural.

Confusion arises over the plural of virus because people mistakenly believe that viri or virii is its Latin plural form, (in the same way that fungus, cactus, and hippopotamus become fungi, cacti, and hippopotami). Virus is one of the few Latin nouns without a Latin plural.

Another Interactive Exercise
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See Also

Unusual pluralsPlural forming table Quirks with forming plurals Forming the plurals of abbreviations Forming the plurals of compound nouns