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Plural of Zoo

by Craig Shrives

The Quick Answer

The plural of "zoo" is "zoos."

The Plural of Zoo

The plural of "zoo" is "zoos."

In the 1970s, zoos began making conservation their central role.
Many of today's zoos hope to stop or slow the decline of many endangered species.

The noun "zoo" adheres to the standard rules for forming the plurals of nouns in English (shown in the table below).

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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	bus dress	add es	buses dresses
Nouns ending [consonant] o	zoo tomato	add either s or es (There are no rules for this - you have to know.)	zoos 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 Zoo?

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:

"Echo" becomes "echoes."
"Torpedo" becomes "torpedoes."

With some words, both versions are accepted. For example:

"Volcano" becomes "volcanoes" or "volcanos."
"Halo" becomes "haloes" or "halos."

The plural of "zoo" is always "zoos." 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 "zoo" becomes "zoos," but "hero" becomes "heroes.")

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:

Young kangaroo's are called joeys.
Young kangaroos are called joeys.

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