Grammar A1–A2 4 min read Updated 10 June 2026

The plural of mouse (the animal) is mice. For computer mouse, both mice and mouses are used, though mice is more common.

Why Is the Plural of Mouse ‘Mice’?

English inherited mouse → mice from Old English, where the singular was mūs and the plural was mýs. The vowel changed to signal plurality, rather than adding a suffix. Over centuries of language change, mūs became mouse and mýs became mice. The relationship between the two forms is now opaque to modern speakers, which is why learners often reach for the logical but incorrect mouses.

This type of vowel change is called ablaut (sometimes called a mutated plural or umlaut plural). It is a genuine grammatical process, not a random irregularity. The same pattern appears in several other common English words:

Singular Plural Vowel change
mousemiceou → i
louseliceou → i
footfeetoo → ee
toothteethoo → ee
goosegeeseoo → ee
manmena → e
womanwomeno → e (in the second syllable)

Notice that mouse → mice shares its exact vowel change with louse → lice. These two pairs are the only common English nouns that use the ou → i ablaut pattern for the plural.

Computer Mouse: Mice or Mouses?

When the computer mouse was named in the 1960s, engineers borrowed the existing word for the small rodent because the device’s cord resembled a tail. The question of what to call two or more of them has been debated ever since.

In practice:

  • Mice is the dominant form in both everyday speech and most published style guides. Most native speakers would say “I need two wireless mice.”
  • Mouses appears in some technical documentation and was endorsed by a small number of style guides during the 1980s and 1990s to distinguish the device from the animal. It has largely fallen out of favour.
  • The Microsoft Manual of Style and Apple Style Guide both use mice.

For everyday English, academic writing, and professional contexts, use mice for both meanings. If there is a genuine risk of ambiguity in a technical text, you can write computer mice to be explicit.

How to Use ‘Mice’ in a Sentence

Because mice is a plural noun, it always takes a plural verb and cannot be preceded by a or an:

  • The mice in the barn were eating the grain. — plural verb
  • Scientists used mice in the laboratory study. — direct object
  • Three wireless mice were ordered for the new workstations. — computer context
  • The cat chased the mice around the room. — definite article with plural

To refer to one animal or one device, use the singular: a mouse, one mouse, the mouse.

Correct and Incorrect Examples

Correct ✓ Incorrect ✗ Note
There are three mice in the trap. There are three mouses in the trap. Animal: only mice is correct.
We bought two new wireless mice. We bought two new wireless mouses. Computer device: mice preferred.
The mice were scurrying across the floor. The mouse were scurrying across the floor. Do not use singular form with plural verb.
I saw a mouse in the kitchen. I saw a mice in the kitchen. Mice is plural; never use with a/an.
Field mice hibernate during winter. Field mices hibernate during winter. Mices does not exist; mice is already plural.
The IT team replaced all the computer mice. The IT team replaced all the computer mouse. Use plural when referring to more than one device.
Memory Tip

Group the irregulars together: one mouse → two mice, just like one goose → two geese. Both follow the same Old English vowel-change rule. If you can remember geese, you will remember mice.

Common Mistakes to Avoid

  • Writing “mouses” for the animal. This is never correct. The animal always takes mice as its plural.
  • Writing “mices”. This does not exist in English. Mice is already the plural; you cannot add a further -s.
  • Using “a mice”. Because mice is plural, it cannot follow the article a or an. Use a mouse for the singular.
  • Using a singular verb with mice. Write the mice are, not the mice is.

Related Grammar: Other Irregular Plurals

Once you know mouse → mice, it is worth learning the other small group of English nouns that change their vowel rather than adding -s:

  • foot → feet — the most common ablaut plural in everyday English
  • tooth → teeth — dental context and figurative uses (by the skin of its teeth)
  • goose → geese — but note: mongoose → mongooses (not mongeese)
  • louse → lice — same ou → i pattern as mouse → mice
  • man → men / woman → women

There is also a separate group of nouns with the same form in singular and plural: sheep, deer, fish, species, series. These are a different type of irregularity from the ablaut group.

Practise with Exercises

The best way to fix irregular plurals in memory is through active practice. These free LexFizz exercises will help:

  • Flash Cards — drill singular–plural pairs including all the common irregulars.
  • Grammar Quiz — multiple-choice questions on irregular plurals at A1–B1 level.
  • Cloze Dropdown — fill in the correct plural form in a sentence context.

For more on confusing noun forms, see our guide to English Grammar for Beginners, which covers regular and irregular plurals in full.

Frequently Asked Questions

What is the plural of mouse?
The plural of mouse (the animal) is mice. For computer mouse, both mice and mouses are used, though mice is more common. In everyday speech and most style guides, mice is the recommended form for both meanings.
Why is the plural of mouse “mice” and not “mouses”?
Mouse is an Old English word that forms its plural through a vowel change (ou → i) rather than by adding -s or -es. This process is called ablaut and is a relic of Germanic language history. Other examples of the same pattern include louse → lice. The forms foot → feet and goose → geese use a similar but slightly different ablaut (oo → ee). Because these plural forms were already fixed when English developed its regular -s plural system, they were simply preserved.
Is “mouses” ever correct?
Mouses occasionally appears for the computer device in some technical publications, particularly older documentation from the 1980s and 1990s. However, it is not accepted for the animal under any circumstances, and even for the device it has fallen out of favour. The major technology style guides (Microsoft, Apple) now use mice. For most learners and writers, it is safest to use mice in all contexts.
What is ablaut, and which English words use it to form plurals?
Ablaut is a systematic vowel change used to show a grammatical difference, inherited from Old and Middle English Germanic roots. The irregular plurals formed by ablaut in modern English are: mouse → mice, louse → lice (ou → i); foot → feet, tooth → teeth, goose → geese (oo → ee); man → men, woman → women (a → e). No new nouns in English form their plural this way; this is a closed historical set.
What is the plural of “computer mouse”?
For the computer input device, mice is preferred in everyday speech, formal writing, and most style guides. The plural mouses was proposed in some early technical guides to distinguish the device from the animal, but the distinction never became standard. Today, the Microsoft Manual of Style and the Apple Style Guide both use mice. If you need to be completely unambiguous, write computer mice.
How do I use “mice” correctly in a sentence?
Mice is a plural noun, so it always takes a plural verb and cannot follow the articles a or an. Correct examples: "The mice were hiding behind the skirting board." "Three wireless mice are available for the workstations." "Researchers studied the behaviour of the mice over six weeks." To refer to one animal or device, use the singular a mouse or the mouse.
Is “mouse” a regular or irregular noun?
Mouse is an irregular noun. Regular English nouns form their plural by adding -s (cat → cats) or -es (box → boxes). Mouse does neither: it changes its vowel to produce mice. This makes it one of only about seven common irregular plurals that use vowel change in modern English, and one that learners at A1–A2 level are expected to know.
What other animals have irregular plurals like mouse → mice?
Goose → geese and louse → lice are the closest: all three use ablaut. Note that moose → moose (unchanged), not moose → meese, despite the tempting analogy with goose → geese. Some animals share singular and plural forms: sheep, deer, fish. Others follow regular -s plurals: cat → cats, dog → dogs, rat → rats. Ox → oxen is another common irregular that uses the Old English -en suffix.
Can I say “a mice”?
No. Mice is always plural and cannot be used with the indefinite articles a or an, which are reserved for singular nouns. "I saw a mice" is incorrect. Use "I saw a mouse" for one animal, or "I saw some mice" / "I saw two mice" for more than one. This is a very common mistake among learners at A1 level, especially those whose first language marks plurality differently.
How do I remember that the plural of mouse is mice?
Group it with the similar pairs: one goose, two geese; one mouse, two mice; one louse, two lice. Noticing that mouse and louse share the same ou → i change can make both easier to remember. You can also use a simple rhyme: "In the house there was a mouse; in the houses there were mice." Practising with flash cards or a fill-in exercise helps fix irregular plurals in long-term memory far more effectively than reading alone.