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4.3: Irregular Plural Nouns

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    Icon of 9 geese flying in a V formationIrregular plurals, unlike regular plurals, don’t necessarily follow any particular pattern—instead, they follow a lot of different patterns. Because of this, irregular plurals require a lot of memorization; you need to remember which nouns belong to which type of pluralization. Mastering irregulars uses a different region of your brain than regular pluralization: it’s an entirely different skill set than regular pluralization. So don’t get too frustrated if you can’t remember the correct plural. If you’re ever in doubt, the dictionary is there for you.

    No Change (Base Plurals)

    The first kind of irregular plural we’ll talk about is the no-change or base plural. In these words, the singular noun has the exact same form as the plural. Most no-change plurals are types of animals:

    • sheep
    • fish
    • deer
    • moose

    Mid-Word Vowel Change

    In a few words, the mid-word vowels are changed to form the plural. This video lists all seven of these words and their plurals.

    Thumbnail for the embedded element "Irregular plural nouns | the MUTANT PLURALS | Grammar | Khan Academy"

    A YouTube element has been excluded from this version of the text. You can view it online here: http://pb.libretexts.org/gw/?p=40

    Note: The plural for a computer mouse (as opposed to the fuzzy animal) can either be mice or mouses. Some people prefer mouses as it creates some differentiation between the two words.

    Plural –en

    And last we have plural –en. In these words –en is used as the plural ending instead of –s or -es.

    • child → children
    • ox → oxen
    • brother → brethren
    • sister → sistren
    Note: Brethren and sistren are antiquated terms that you’re unlikely to run into in your life; however, since these are the only four words in English that use this plural, all four have been included above.

    Practice

    What are the correct plurals for the following words?

    Singular Plural Singular Plural
    goose [practice-area rows=”1″][/practice-area] moose [practice-area rows=”1″][/practice-area]
    fish [practice-area rows=”1″][/practice-area] child [practice-area rows=”1″][/practice-area]
    man [practice-area rows=”1″][/practice-area] tooth [practice-area rows=”1″][/practice-area]

    [reveal-answer q=”245006″]Show Answer[/reveal-answer]
    [hidden-answer a=”245006″]

    Singular Plural Singular Plural
    goose geese moose moose
    fish fish child children
    man men tooth teeth

    [/hidden-answer]

    Borrowed Words –i, –en, –a, –es, –ae

    The last category of irregular plurals is borrowed words. These words are native to other languages (e.g., Latin, Greek) and have retained the pluralization rules from their original tongue.

    Singular –us; Plural –i

    • cactus → cacti
    • fungus → fungi
    • syllabus → syllabi

    In informal speech, cactuses and funguses are acceptable. Octopuses is preferred to octopi, but octopi is an accepted word.

    Singular -a; Plural –ae

    • formula → formulae (sometimes formulas)
    • vertebra → vertebrae
    • larva → larvae

    Singular –ix, –ex; Plural –ices, –es

    • appendix → appendices (sometimes appendixes)
    • index → indices

    Singular –on, –um; Plural –a

    • criterion → criteria
    • bacterium → bacteria
    • medium → media

    Singular –is; Plural –es

    • analysis → analyses
    • crisis → crises
    • thesis → theses

    Practice

    What are the correct plurals for the following words?

    Singular Plural Singular Plural
    memorandum [practice-area rows=”1″][/practice-area] emphasis [practice-area rows=”1″][/practice-area]
    focus [practice-area rows=”1″][/practice-area] basis [practice-area rows=”1″][/practice-area]
    nucleus [practice-area rows=”1″][/practice-area] phenomenon [practice-area rows=”1″][/practice-area]
    appendix [practice-area rows=”1″][/practice-area] curriculum [practice-area rows=”1″][/practice-area]
    parenthesis [practice-area rows=”1″][/practice-area] hypothesis [practice-area rows=”1″][/practice-area]
    stimulus [practice-area rows=”1″][/practice-area] vertebra [practice-area rows=”1″][/practice-area]

    [reveal-answer q=”245005″]Show Answer[/reveal-answer]
    [hidden-answer a=”245005″]

    Singular Plural Singular Plural
    memorandum memoranda emphasis emphases
    focus foci (focuses is also acceptable) basis bases
    nucleus nuclei phenomenon phenomena
    appendix appendices (appendixes is also acceptable) curriculum curricula
    parenthesis parentheses hypothesis hypotheses
    stimulus stimuli vertebra vertebrae

    [/hidden-answer]

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