English grammar

Module 1, Nouns, Lesson 5:

Irregular Plural Nouns

English grammar

Irregular nouns form plurals in unusual ways. Dictionaries will give you the plural spelling if it is irregular.

one fish ... two fish
one sheep ... two sheep
one deer ... two deer
one child ... two children
one foot ... two feet
one tooth ... two teeth
one man ... two men

Nouns from Latin and Greek make plurals in strange ways. Nouns with similar endings form plurals in similar ways. Some have changed to just add s because most people don't know any better. Impress your friends and family by knowing the correct forms.

amoeba ⇒ amoebae
antenna ⇒ antennae
alumna ⇒ alumnae
alumnus ⇒ alumni
cactus ⇒ cacti
fungus ⇒ fungi
nucleus ⇒ nuclei
octopus ⇒ octopi
die ⇒ dice
analysis ⇒ analyses
axis ⇒ axes
diagnosis ⇒ diagnoses
hypothesis ⇒ hypotheses
parenthesis ⇒ parentheses
criterion ⇒ criteria
phenomenon ⇒ phenomena

Some nouns exist only in the plural form.

pants, binoculars, shorts, tweezers, scissors ...

Making letters, numbers, and abbreviations plural follows different rules depending on the style manual you are using.

  • Some style manuals have you add a lowercase s. An apostrophe is used for letters to distinguish between the letter and a word (a versus as). Some manuals also use an apostrophe for numbers.

    A's, 2's, CDs, M.D.s

  • Newer manuals have you add an italic, lower-case s without the apostrophe for letters.

    As, 2s, CDs, M.D.s

When writing, consult your manual if you have one. Whether you have a manual or not, make sure to follow the same rule throughout the piece.

Practice What You've Learned

English grammar
Click the word that is the correct plural form of the noun in bold.
larva - larvas ... larvaes ... larvae ... larvi
trout - trouts ... troutes ... trout ... trouta
bison - bisons ... bisones ... bisonae ... bison
moose - moose ... mooses ... meese ... moosae
salmon - salmons ... salmon ... salmonae ... salmoni
mouse - mouses ... mice ... meese ... mousi
formula - formulaes ... formula ... formulae ... formuli
nucleus - nucleuses ... nuclea ... nuclei ... nucleum
crisis - crisises ... crisi ... crises ... crisea
stimulus - stimulus ... stimuluses ... stimulae ... stimuli