Double plural

A double plural is a plural form to which an extra suffix has been added, mainly because the original plural suffix (or other variation) had become unproductive and therefore irregular. So the form as a whole was no longer seen as a plural, an instance of morphological leveling. For example, if "geese" (the plural) became the word for "goose" (the singular) in a future version of English, a word geeses might become the licit plural form.

Examples of this can be seen in the history of English and Dutch. Historically, the general English plural markers were not only -s or -en but also (in certain specific declensions) -ra/-ru (which is still rather general today in German under the form -er). The ancient plural of child was "cildra/cildru", to which an -en suffix was later added when the -ra/-ru became unproductive; the Dutch plural form kind-er-en and the corresponding Zeelandic form kind-er-s are also double plurals which were formed in the same way as the English double plurals, while for example German and Limburgian have (historically conservative) single plurals such as Kind-er.

Breeches is an example involving an old plural that did not use a suffix. It was formerly breech which came from Old English brec which was the plural of broc. Another example of this is the term "peoples" which is used to refer to multiple groups of people.