A List of 100 Irregular Plural Nouns in English

Most English nouns form their plural by adding either -s (books, bands, bells) or -es (boxes, bunches, batches). These plural forms are said to follow a regular pattern.

There are no easy rules, unfortunately, for irregular plurals in English. They simply have to be learnt and remembered.
(S. Curtis and M. Manser, The Penguin Writer's Manual, 2002)

But not all nouns conform to this standard pattern. In fact, some of the most common English nouns have irregular plural forms—such as woman/women and child/children.

(The reasons for this are briefly discussed in the article Plural Forms of English Nouns.) In addition, several nouns have alternative plurals, one regular and the other irregular.

In regard to these alternative forms, there are no strict rules to guide our use of them:

People have to learn which form to use as they meet the words for the first time, and must become aware of variations in usage. When there is a choice, the classical [irregular] plural is usually the more technical, learned, or formal, as in the case of formulas vs. formulae or curriculums vs. curricula. Sometimes, alternative plurals have even developed different senses, as in the cases of (spirit) mediums vs. (mass) media, or appendixes (in bodies or books) vs. appendices (only in books).
(David Crystal, The Cambridge Encyclopedia of the English Language, 2nd ed. Cambridge University Press, 2003)

As you'll see in the list that follows, many words with irregular plurals are loanwords that have kept their foreign plural forms (or at least held on to those forms as alternatives to regular English plurals).

List of 100 Irregular Plural Nouns in English

In the list below, you'll find singular noun forms in the left column and the corresponding plural forms in the right column. When a noun has more than one plural form, the irregular one appears first, though that doesn't necessarily mean that the irregular form is more widely accepted than the regular form.

Sources

The plural forms in this list are recognized by Merriam-Webster's Collegiate Dictionary (2003) and The American Heritage Dictionary of the English Language (2011).