Plural of Cactus

What Is the Plural of Cactus?

The Quick Answer

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.

Table of Contents

Are You Good at Plurals?
The Standard Rules for Forming the Plurals
Why Is There Confusion over the Plural of Cactus?
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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	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	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	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.)