Grammar Monster
Grammar Monster

Plural of Virus

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).

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 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 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.