Irregular Plural Nouns

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.

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