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. correct tick
  • Many of today's zoos hope to stop or slow the decline of many endangered species. correct tick
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 (small British flag)
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
Read more about English spelling rules.

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. wrong cross
  • Young kangaroos are called joeys. correct tick
Read more about apostrophes and plurals.
Read more about using apostrophes.

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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