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Plural of Cactus

The Quick Answer
The plural of cactus is cacti or cactuses.

The Plural of Cactus

The plural of cactus is cacti or cactuses.
  • Most cacti live in habitats subject to at least some drought.
  • The great majority of cactuses have no visible leaves.
The noun cactus has a Latin root, which is the derivation of the plural cacti. Through common usage, cactuses (which adheres to the standard rules for forming plurals) is also acceptable.

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 cactus
dress
add es cactuses
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 cactus
medium
some nouns adopt foreign rulings cacti
media

Why Is There Confusion over the Plural of Cactus?

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

Both cactuses and cacti are acceptable. Of note, cacti is the more common plural. (See the evidence in Google's Ngram Viewer.)