I don't understand these... why?

Why does it make difference when original form is almost same? (there's only just one letter difference, House and Mouse)

And I learned that computer's mouse's plural form can be both mouses and mice and it's confusing me so much.

  • 10
    The short answer is that English is an irregular language which has evolved from several influences. Nobody sat down and designed it. Commented Dec 3, 2021 at 6:41
  • 2
    You can look up the etymology of mouse and house. I'm not going to bother, but I'm sure it wouldn't be hard to establish how it comes about that the two nouns follow difference rules for deriving the plural form (mouse/mice, louse/lice, OR house/houses, spouse/spouses). Which last example cries out for a pun based on the idea that having multiple spouses adds spice to the bigamist's life. Commented Dec 3, 2021 at 14:11
  • 1
    Interesting. I wasn't aware that "mouses" was considered to be a correct alternative when it came to computer mice, but Lexico and M-W confirm it (although Collins and Cambridge beg to differ). I would always say "mice".
    – rjpond
    Commented Dec 3, 2021 at 21:36
  • @rjpond Oh, yeah. I should have wrote that sources in my OP, thanks for that.
    – Skye-AT
    Commented Dec 4, 2021 at 14:36

1 Answer 1


There is no "logic" to it. English has irregular nouns. You must remember the nouns that have this kind of plural. Fortunately it is a short list:

man-men, foot-feet, tooth-teeth, goose-geese, louse-lice, mouse-mice, and woman-women

Now you could ask why these nouns are irregular. The reason is different patterns of mutation and regularisation.

There is a pattern called "i-mutation. A back vowel like [u] tends to be raised towards [i] when followed by a raised vowel. Listen carefully to the the sound in "doing" (when spoken naturally and quickly). The word "doing" becomes pronunced as something like [diwin]. The [i] of "ing" causes the [u] to become raised.

A similar thing happened to Old English "mus" = "mouse". The plural /musiz/ became /misiz/. Then vowel changes took /mus/ to /maus/ and /misiz/ to /maisiz/. The plural ending wasn't needed and lazy speakers dropped the /-iz/ to make the plural /mais/ (which was spelled mice). You can read more about i-mutation

House, on the other hand underwent regularisation. Instead of the plural evolving towards an irregular form, it changed to the regular. There is no particular logic to why "house" was regularised, but "mouse" was mutated. However "house" resisted the change to /haisiz/ and took the regular plural. The tendency for irregular forms to become regular opposes the tendency of words to mutate. This tension gives rise to illogical pairs like "mice"/"houses".

The use of computer mouses is another example of regularisation. With the change in meaning comes "permission" (from the gods of grammar) to reconsider the plural and regularise the grammar. Some people have taken this opportunity. But most don't and the common plural of "computer mouse" is still "computer mice".

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