Plural of “mouse”

The plural of mouse is mice.

Why

"Mouse" and its plural "mice" descend from Old English "mus" and "mys," reflecting a genuine Germanic sound process called i-mutation (or umlaut): an old plural ending, since lost, once pulled the root vowel forward in the mouth before the ending itself disappeared entirely, leaving the vowel shift as the sole remaining plural marker. The same historical mechanism produced foot/feet, tooth/teeth, and goose/geese.

This mutation pattern is ancient enough to predate written English entirely and is shared, in related forms, across other Germanic languages — German "Maus/Mäuse" shows a parallel (though not identical) vowel-shift plural, confirming the process goes back to a common Germanic ancestor rather than developing independently within English. The animal sense of "mouse" also appears in a wide range of idioms that keep the singular form fixed regardless of how many mice are actually implied — "quiet as a mouse," "cat and mouse," "mousy" as an adjective for a timid personality — none of which pluralize even when describing a general trait rather than one specific animal.

Usage note

The computer-peripheral sense of "mouse" (coined in the 1960s, from its cord resembling a tail) is genuinely ambiguous in its plural: "computer mice" is by far the more common and widely accepted form, following the animal's irregular plural, but "mouses" does appear in some technical writing and is listed as an acceptable alternative in a few dictionaries specifically for the device, distinct from the animal. The metaphor also runs in the other direction: "mousetrap" and "mouse hole" keep the singular form as a compound noun regardless of how many mice are actually involved, treating "mouse" here as a descriptive modifier rather than as a countable noun referring to a specific number of animals.

In video-game and tech-review writing specifically, "mice" for multiple computer mice has become close to universal, likely because tech writers are disproportionately careful, detail-oriented writers who default to the historically consistent animal plural rather than treating the device as a wholly separate noun needing its own rule. In biomedical research specifically, "mice" is a specialized term of art referring to entire genetically defined strains used in experiments ("the mice were bred for diabetes research"), a scientific register where the plural form is used constantly and precisely, distinct from its everyday sense describing a small number of household rodents.

Common real mistakes

Using "mouses" for the animal is a straightforward error; the debate over "mouses" vs. "mice" only genuinely applies to the computer device, where usage hasn't fully settled the way it has for the animal. Retail listings for the device lean toward the plain "mouses" more often than editorial or review writing does, so the choice here often comes down to a publication's own house style rather than any industry-wide consensus.

The wider pattern

The same vowel-mutation mechanism produced "louse/lice," "foot/feet," "tooth/teeth," "goose/geese," and "man/men" — a small, closed set of very old, very common Germanic nouns; no new noun entering English today acquires this kind of plural, since the sound process that created it stopped being active in the language over a thousand years ago.

Examples

• The old barn was full of field mice.
• She bought two wireless mice for the office computers.
• A single mouse can chew through surprisingly tough material.
• The cat chased the mice out from under the porch.
• Both mice on my desk need new batteries.
• Scientists use lab mice extensively in genetic research.
• The mice scurried away when the light came on.
• She set a trap for the mice in the attic.
• Wireless mice are more convenient for laptop users.
• The lab tracked the mice through a small maze.
• Two mice darted behind the refrigerator before anyone could react.