Rules for Plural Nouns - Here is a simple poster to help kiddies understand the different rules when changing nouns from singular form to plural form. There are obviously always exceptions to every rule, however these rules apply in most cases.
This tricky noun packet includes 40 different irregular noun forms with their matching plurals for a total of 80 cards. This is a really fun unit, especially the card match. My kids actually raced to see how many they could get.