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.
Read more about apostrophes and plurals.
Read more about using apostrophes.
Another Interactive Exercise
Here are three randomly selected questions from another exercise on plurals, which can be edited, printed to create an exercise worksheet, or sent via email to friends or students.

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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