# irregular-plurals > Map of nouns to their irregular plural form > An irregular plural in this library is defined as a noun that cannot be made plural by applying these rules: > - If the noun ends in an "s", "x", "z", "ch" or "sh", add "es" > - If the noun ends in a "y" and is preceded by a consonant, drop the "y" and add "ies" > - If the noun ends in a "y" and is preceded by a vowel, add "s" The list is just a [JSON file](irregular-plurals.json) and can be used anywhere. ## Install ``` $ npm install irregular-plurals ``` ## Usage ```js const irregularPlurals = require('irregular-plurals'); console.log(irregularPlurals.get('cactus')); //=> 'cacti' console.log(irregularPlurals); /* Map { [addendum, 'addenda'], [alga, 'algae'], … } */ ``` ## Related - [plur](https://github.com/sindresorhus/plur) - Pluralize a word