Irregular Plural Nouns
Most English nouns make their plural with -s or -es: cat becomes cats, box becomes boxes. Irregular plurals break that rule in a handful of old, patterned ways: the vowel changes (man/men, foot/feet, tooth/teeth, goose/geese, mouse/mice), the word stays identical (fish, sheep), or an ancient ending appears (child/children).
These are not random exceptions. The vowel-change plurals are survivors from Old English, and they cluster in the oldest words in the language: people, body parts, and animals. The words children use most kept their thousand-year-old plurals.
The list below comes from our Grade 3 spelling curriculum, grouped so the patterns show, with printables and free online practice for every word.
The rule
Irregular plurals change in one of three main ways instead of adding -s: the inside vowel shifts (man/men, foot/feet, mouse/mice), the word stays the same (fish, sheep), or an old ending attaches (child/children). A few borrowed words keep foreign plurals (cactus/cacti).
Irregular Plural Nouns by grade, from our curriculum
These are the exact lists our K-6 spelling curriculum teaches. Every list links to free online practice and printable worksheets - no account needed.
Irregular Plural Nouns
Grade 3- children
- feet
- teeth
- mice
- men
- women
- geese
- cacti
- fish
- sheep
How the pattern works
The vowel-change group is the big one: men, women, feet, teeth, geese, mice. These all come from an Old English sound pattern, and because the words are so frequent, the old plurals never got replaced. They are learned as pairs: one foot, two feet.
The no-change group (fish, sheep, deer) is mostly animals that were herded, hunted, or caught. The sentence carries the number instead: one sheep, five sheep.
Cacti is a borrowed Latin plural - and cactuses is also accepted in modern English. Our list teaches cacti, and it is worth telling students that both appear in real books, because honesty about variation builds trust in the rules that are firm.
Common mistakes to watch for
- Adding -s to the singular anyway ("foots", "childs", "sheeps") - the natural first guess, and the sign that the regular rule is nicely learned.
- Double plurals ("childrens", "feets", "mens") - the irregular form already is plural, so nothing more attaches.
- Writing "womans" for women - the sound changes in the first syllable while the spelling changes in the second (a becomes e), making women the trickiest word on the list.
- Adding -es to fish in everyday writing ("fishes") - fish is its own plural; "fishes" survives only in special uses, like talking about several species.
Example sentences
- children - The children lined up before the bell rang.
- feet - Wet feet squeaked all the way down the hall.
- mice - Two mice darted behind the compost bin.
- sheep - The sheep grazed on the hillside all afternoon.
- women - Three women from the fire station visited our class.
Taught in Grade 3 in our curriculum. Because these plurals appear constantly in reading, most students already say them correctly - the work is matching the spelling to the word they already know by ear.
Frequently asked questions
What is an irregular plural noun?
A noun whose plural is not made with -s or -es: man/men, foot/feet, tooth/teeth, mouse/mice, child/children, sheep/sheep. The change happens inside the word, or not at all.
Why does English have irregular plurals?
They are survivors of Old English plural patterns. The most frequently used words (people, body parts, animals) resisted the newer -s rule, which is why the irregulars are all common words.
Is cactuses wrong?
No. Cacti is the borrowed Latin plural and cactuses is the regular English one; dictionaries accept both. Our curriculum teaches cacti, and students should recognize either in reading.
Is fishes ever correct?
In everyday writing the plural of fish is fish. Fishes appears in special contexts, mainly when talking about multiple species of fish, so students will occasionally meet it in science books.
Turn these lists into practice in one click
Free spelling games, tests, and printables for every list above - built for K-6 classrooms and home practice. No signup, no cost.