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Plural of Volcano

The Quick Answer
The plural of volcano is volcanoes or volcanos.

The Plural of Volcano

The plural of volcano is volcanoes or volcanos.
  • The study of volcanoes is called volcanology.
  • Volcanos are often considered to be extinct if there are no written records of its activity.
The noun volcano 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 bus
dress
add es buses
dresses
Nouns ending [consonant] o volcano
zero
tomato
add either s or es
(There are no rules for this - you have to know.)
volcanoes or volcanos
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 storey ()
donkey
add s storeys
donkeys
Nouns ending f or fe dwarf
knife
ves and/or s
(There are no rules - you have to know.)
dwarfs
knives
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

Why Is There Confusion over the Plural of Volcano?

There is confusion because the rule for forming plurals with nouns ending in o isn't straightforward. Most nouns will just add an s. For example:
  • Kangaroo becomes kangaroos.
  • Piano becomes pianos.
Some add es. For example:
  • Embargo becomes embargoes.
  • Torpedo becomes torpedoes.
With some words, both versions are accepted. For example:
  • Halo becomes haloes or halos.
  • Echo becomes echoes or echos.
The plural of volcano can be either volcanoes or volcanos. Unfortunately, there is no clever way of knowing which nouns ending o follow which rules. You have to know. (For example, you have to know that solo becomes solos, but tomatos becomes tomatoes.)

Even though volcanoes and volcanos are both accepted plurals, volcanoes is by far the more common of the two. (See the difference in Google's Ngram Viewer.)
Beware

Don't Use an Apostrophe to Form a Plural

Adding 's is never an option when forming the plural of a noun. Despite this simple rule, inexperienced writers often feel compelled to add an apostrophe, especially when the noun ends with a vowel (e.g., piano, tomato, emu). For example:
  • The tomato's were ripe.
  • The tomatoes were ripe.
Read more about apostrophes and plurals.
Read more about using apostrophes.