What is the difference between "mouse" and "mice"?

The difference between mouse and mice is grammatical number, mouse is singular and mice is plural, and they refer to the same animal or object in different quantities. Mouse refers to one, for example I saw a mouse in the kitchen or I need a new computer mouse. Mice refers to two or more, for example I saw three mice in the attic or the computer lab has twenty mice. This is an example of an irregular plural in English that does not follow the standard rule of adding s or es. Instead, the vowel changes from ou to i, similar to louse to lice and goose to geese, a pattern inherited from Old English. The distinction applies to both the animal Mus musculus and the computer pointing device, although some people informally say computer mouses for the device, the traditional and still preferred plural even for computers is computer mice according to most dictionaries and style guides. You would never say two mouse or one mices, those are incorrect. In verb agreement, mouse takes a singular verb, the mouse is hiding, while mice takes a plural verb, the mice are hiding. Understanding this difference is important for clear writing and speaking, especially when reporting pest problems or talking about technology.