Irregular Plurals In English
It's important to note that many of these irregular plurals are optional and the standard "-s" plural is also acceptable for many words such as brothers, formulas, viruses, forums, indexes, etc.
| Singular | Irregular Plural |
|---|---|
| bison | bison |
| buffalo | buffalo |
| deer | deer |
| fish | fish |
| moose | moose |
| pike | pike |
| sheep | sheep |
| salmon | salmon |
| trout | trout |
| swine | swine |
| plankton | plankton |
| ox | oxen |
| child | children |
| brother | brethren |
| dwarf | dwarfs/dwarves |
| hoof | hoofs/hooves |
| elf | elfs/elves |
| foot | feet |
| goose | geese |
| louse | lice |
| man | men |
| mouse | mice |
| tooth | teeth |
| woman | women |
| person | people |
| die | dice |
| penny | pence |
| alumna | alumnae |
| formula | formulae |
| index | indices |
| matrix | matrices |
| vertex | vertices |
| axis | axes |
| crisis | crises |
| testis | testes |
| series | series |
| species | species |
| automaton | automata |
| criterion | criteria |
| phenomenon | phenomena |
| polyhedron | polyhedra |
| addendum | addenda |
| corrigendum | corrigenda |
| datum | data |
| forum | fora |
| medium | media |
| memorandum | memoranda |
| millennium | millennia |
| ovum | ova |
| spectrum | spectra |
| alumnus | alumni |
| corpus | corpora |
| census | censuses |
| focus | foci |
| genus | genera |
| prospectus | prospectuses |
| radius | radii |
| campus | Campuses |
| succubus | succubi |
| stylus | styli |
| syllabus | syllabi |
| viscus | viscera |
| virus | virii |
| cactus | cacti |
| fungus | fungi |
| hippopotamus | hippopotami |
| terminus | termini |
| uterus | uteri |
| stigma | stigmata |
| stoma | stomata |
| schema | schemata |
| dogma | dogmata |
| beau | beaux |
| bureau | bureaux |
| château | châteaux |
| tableau | tableaux |
| cherub | cherubim |
| seraph | seraphim |
| kibbutz | kibbutzim |
