Plural of Stimulus

by Craig Shrives
The Quick Answer
The plural of stimulus is stimuli.

The Plural of Stimulus

The plural of stimulus is stimuli.
  • In art, stimuli are things that interests artists and give them new ideas.
  • Rapid changes, called stimuli, provoke reactions in living organisms that are often very different from those expected from non-living things. (Professor John Blamire)
The noun stimulus has a Latin root, which is the derivation of the plural stimuli. Stimuluses (which adheres to the standard rules for forming plurals) is not an accepted plural.

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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 dress
stimulus
add es dresses
stimuluses
(Just like nucleus (plural nuclei), stimulus does not form its plural using the standard rules of English.)
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 stimulus
medium
some nouns adopt foreign rulings stimuli
media

Why Is There Confusion over the Plural of Stimulus?

Confusion arises over the plural of stimulus because its plural form (stimuli) derives from Latin, and native English speakers are unsure whether stimuluses, which adheres to the standard ruling for forming plurals, has come into use. Many words with Latin roots (e.g., nucleus, stadium, referendum) have either adopted a standard plural ending alongside the Latin one or have dropped the Latin one entirely (e.g., referendums but referenda ).

Unlike these words, stimuluses is not an accepted plural. You must use stimuli.

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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

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